What is the main difference between a subway and a metro system?

The main difference is that a subway is a specific type of metro system that runs entirely underground, whereas a metro system is a broader term for any urban rapid transit rail network that can run underground, at grade, or on elevated tracks.

Are subway and metro systems the same thing?

No, they are not the same thing because a subway is always a metro, but a metro is not always a subway, as metro networks often include above-ground and elevated sections in addition to underground tunnels.

Which is better for a city, a subway or a metro system?

Neither is inherently better because the choice depends on a city's geography, budget, and density, with subways offering land savings in crowded downtowns while metros with surface lines cost significantly less per mile to build.

Is it more expensive to build a subway than a metro system?

Yes, building a subway is typically more expensive because tunneling costs can reach hundreds of millions of dollars per mile, whereas at-grade metro tracks cost a fraction of that amount to construct.

Are subways safer than metro systems?

Subways are generally safer than surface-level metro systems because underground tracks are fully segregated from road traffic, pedestrians, and weather hazards, eliminating the risk of grade-crossing collisions and falling debris.

Can a metro system run entirely underground like a subway?

Yes, a metro system can run entirely underground, and when it does, it is correctly classified as a subway, such as the London Underground or the New York City Subway.

What is a common beginner mistake when using subway and metro terms?

A common beginner mistake is assuming the terms are interchangeable globally, when in reality a subway specifically refers to underground rail while metro is the generic category, and many cities use the words based on local convention rather than technical accuracy.

Can you use a subway ticket to ride a metro system?

Yes, you can use a subway ticket to ride a metro system because a subway is a component of the larger metro network, so the same fare and ticket are valid for all lines within that unified system.

Why do some cities call their underground rail a metro instead of a subway?

Some cities call their underground rail a metro instead of a subway because the term metro is a shortened form of metropolitan railway that gained popularity in Paris and is now the standard international name for urban rapid transit networks.

Can I switch from riding a subway to a metro system on the same trip?

Yes, you can switch from riding a subway to a metro system on the same trip because they are part of one integrated network, and transfers between underground and above-ground sections are common and usually free within the same fare zone.

Difference Between

Difference Between Subway and Metro Systems

Written byNex Virox Team

Editorial Team

Reviewed byVarshal Nirbhavane

Senior SEO & Organic Growth Professional · 5+ years

Published: August 28, 202619 min read

Quick answer

The main difference between Subway and Metro Systems is that a subway is an underground urban rail line, while a metro system is a broader, often elevated or at-grade rapid transit network. Subway is an underground train system, while Metro Systems are city-wide electric railways that may run above ground.

Key takeaways

Core distinction: Subway refers specifically to underground rail, while metro systems may run above ground.
How each works: Subways operate exclusively in tunnels beneath cities, whereas metros use elevated, surface, or underground tracks.
Cost and effort: Building subways costs significantly more per mile than constructing metro lines on elevated or surface routes.
Best-fit use case: Choose subways for dense downtown cores, but metros for broader metropolitan regions with varied terrain.
Common decision mistake: Using subway and metro interchangeably ignores critical engineering, cost, and operational differences between the two transit types.

Table of Contents18 sections

Difference Between Subway and Metro Systems: Comparison Table

Aspect	Subway	Metro Systems
Definition	An electric railway built predominantly underground within a single city's core.	A high-capacity public rail network serving a city and its surrounding metropolitan region.
Core Purpose	Moves commuters quickly through dense urban tunnels avoiding surface traffic congestion.	Connects central business districts with residential suburbs and key regional transfer hubs.
Primary Mechanism	Relies on third-rail electrification and tunnel boring to bypass street-level obstacles.	Uses segregated right-of-way with grade-separated tracks, often elevated or at surface level.
Track Location	Runs almost exclusively in deep or shallow underground tunnels beneath city streets.	Operates on a mix of underground, elevated viaducts, and dedicated surface corridors.
Service Area	Limited to a compact urban footprint, typically within 10-15 km of downtown.	Extends 30-60 km outward to integrate satellite towns and suburban employment zones.
Station Spacing	Stations sit 500-1,000 meters apart to serve high-density pedestrian zones.	Stations are spaced 1.5-3 km apart to maximize regional travel speed.
Train Frequency	Headways run as tight as 2-3 minutes during peak commuting hours.	Peak frequencies typically range from 3-6 minutes across branch lines.
Carriage Capacity	Trains carry 600-1,200 passengers using shorter, lighter rolling stock.	Longer consists move 1,500-3,000 riders per train on trunk corridors.
Average Speed	Commercial speeds average 30-40 km/h due to frequent station stops.	Reaches 45-60 km/h average because longer station gaps reduce dwell impact.
Maximum Speed	Top operational speed is typically capped near 80-90 km/h.	Design speeds often reach 100-120 km/h on express or suburban sections.
Construction Cost	Tunnel boring pushes capital costs to $500 million-$1 billion per km.	Elevated or surface alignment lowers costs to $100-300 million per km.
Build Timeline	Deep tunneling extends project delivery to 8-15 years per line.	At-grade sections allow phased opening within 4-8 years.
Infrastructure Depth	Requires ventilation shafts, emergency exits, and waterproofing at depth.	Needs viaduct piers, noise barriers, and level-crossing elimination.
Network Density	Offers fine-grained coverage with 20-40 stations per 10 km².	Provides coarser coverage with 5-15 stations per 10 km².
Operational Cost	Energy-intensive lighting and pumping raise per-km running expenses.	Surface operations reduce energy use for lighting and climate control.
Fare Structure	Flat or short-distance zonal fares dominate single-city subway tariffs.	Distance-based or multi-zone pricing reflects longer regional journeys.
Accessibility	Deep platforms require extensive elevator banks and long underground passages.	Surface-level platforms simplify step-free access and emergency evacuation.
Passenger Comfort	Enclosed tunnels limit natural light and fresh air circulation.	Elevated and surface sections provide daylight and better ventilation.
Signal System	Uses communications-based train control for high-frequency automated operation.	Employs fixed-block or ETCS signaling suited to mixed-speed corridors.
Power Supply	Third-rail DC traction dominates due to tight tunnel clearances.	Overhead catenary AC or DC power is common on open-air segments.
Safety Systems	Platform screen doors and tunnel ventilation are critical fire-safety measures.	Level-crossing protection and grade separation prevent vehicle collisions.
Weather Resilience	Underground operation continues unaffected by snow, ice, or high winds.	Surface and elevated tracks face delays from lightning and fallen trees.
Integration Ease	Connects seamlessly with bus networks but rarely links to intercity rail.	Often shares stations with commuter rail, airports, and national services.
Expansion Flexibility	Extending tunnels under built-up areas faces severe geotechnical constraints.	Adding surface branches to greenfield land is simpler and cheaper.
Land Disruption	Minimizes surface land take but requires large underground construction sites.	Elevated structures cast shadows and create visual intrusion on streets.
Typical Examples	New York City Subway, London Underground, and Moscow Metro fit this type.	Paris RER, Munich U-Bahn, and Hong Kong MTR exemplify regional metro networks.
Primary Ridership	Daily commuters and tourists moving within a dense urban core.	Suburban workers and inter-district travelers covering longer distances.
Key Limitation	High construction cost prevents serving low-density outer neighborhoods.	Wide station spacing creates poor walkability for local short trips.
Best-Fit Scenario	Choose a subway for high-frequency movement inside a compact, dense downtown.	Choose metro systems for regional connectivity across a sprawling metropolitan area.

What Is Subway?

Subway is an electric railway system built underground in dense urban areas. It moves large passenger volumes quickly beneath city streets, avoiding surface traffic congestion. Subways exist to provide fast, reliable, high-capacity transit where ground-level space is scarce.

Definition of Subway

A subway is a grade-separated urban rail transit line where the majority of track is located in underground tunnels. It operates on exclusive right-of-way with no level crossings, enabling frequent, high-speed service independent of road traffic. Subways serve as the backbone of metropolitan public transport networks.

Key Characteristics of Subway

Characteristic	What It Means in Practice
Underground alignment	Most track runs in tunnels beneath streets, reducing land acquisition costs and noise above ground.
Exclusive right-of-way	Trains operate on dedicated tracks with no road intersections, guaranteeing consistent travel times.
Electric traction	Third-rail or overhead catenary power eliminates diesel emissions and enables rapid acceleration.
High passenger capacity	Long trains with multiple cars move 30,000 to 80,000 passengers per hour per direction.
Frequent service	Headways of 2 to 5 minutes during peak hours create a walk-up-and-board experience.
Grade-separated stations	Platforms are reached by stairs, escalators or elevators, keeping passengers clear of train tracks.
Fixed guideway	Steel wheels on steel rails provide predictable, low-friction movement over long distances.
Central city focus	Lines concentrate on downtown cores and high-density corridors where demand is greatest.
High construction cost	Tunnel boring and deep stations require billions in capital investment per line.
24-hour potential	Automated signalling allows overnight maintenance windows while still supporting late-night service.

Common Examples of Subway

London Underground – the world's oldest underground railway, opened in 1863, spanning 272 stations.
New York City Subway – one of the largest systems globally with 472 stations and 24-hour service on most lines.
Moscow Metro – famous for ornate station architecture and extremely short peak headways of 90 seconds.
Tokyo Metro – carries over 7 million daily passengers across 9 densely connected underground lines.
Paris Métro – a compact system where station spacing averages just 548 metres, ideal for short hops.
Hong Kong MTR – a profitable subway known for punctuality and seamless integration with shopping centres.
Beijing Subway – the world's longest subway network with over 800 kilometres of operational track.
Berlin U-Bahn – a German system where most lines run underground but some surface sections exist in outer areas.
Madrid Metro – one of Europe's densest networks, ranking among the top ten longest globally.
Singapore MRT – a fully automated, driverless subway on the North East Line, opened in 2003.

Advantages and Limitations of Subway

Advantages	Limitations
Eliminates surface traffic delays entirely, offering journey times that buses cannot match.	Construction costs routinely exceed $500 million per kilometre, making expansion slow and politically difficult.
Moves tens of thousands of passengers per hour on a single corridor without adding road vehicles.	Deep stations require long escalator rides, adding 3 to 5 minutes to every trip compared to surface transit.
Reduces per-passenger carbon emissions dramatically versus private cars, supporting climate goals.	Fixed underground routes cannot adapt to changing travel patterns or new neighbourhood growth quickly.
Operates reliably in extreme weather since tunnels shield trains from snow, heat and flooding.	Flooding and fire risks in tunnels demand expensive ventilation, drainage and evacuation systems.
Provides accessible transport for people who cannot drive, including seniors and disabled riders.	Elevator outages at older stations leave many platforms inaccessible despite legal accessibility mandates.
Raises property values near stations, encouraging dense, walkable urban development.	Night-time maintenance windows are short, forcing service closures that inconvenience late-shift workers.
Uses electricity that can come from renewable sources, unlike diesel buses or petrol cars.	Vibration from trains transfers through tunnels to nearby buildings, causing structural and noise complaints.
Offers high-frequency service that reduces waiting time to minutes even during off-peak hours.	Overcrowding at central interchange stations creates dangerous platform congestion during peak commuting.
Creates a permanent civic asset that serves multiple generations over a 100-year lifespan.	Signalling and rolling stock upgrades require full line closures, disrupting millions of daily riders.
Reduces road congestion and accident rates by shifting trips away from surface streets.	Homelessness and petty crime in stations require constant policing, adding recurring operational expense.

What Is Metro Systems?

Metro systems are high-capacity electric rail networks built in tunnels, on elevated tracks, or in reserved cuttings that move large numbers of people quickly through dense urban areas. They exist to bypass street-level traffic congestion and provide reliable, frequent transit for millions of daily commuters.

Definition of Metro Systems

Metro systems are grade-separated urban railways operating on exclusive rights-of-way with no level crossings, using electric multiple-unit trains on fixed routes with frequent scheduled service. They achieve high average speeds and short headways by eliminating interference from road traffic, pedestrians, and other rail services.

Key Characteristics of Metro Systems

Characteristic	What It Means in Practice
Full grade separation	Track runs in tunnels or on viaducts so trains never share space with cars, buses, or pedestrians.
Electric traction	Trains draw power from third rails or overhead wires, producing zero local exhaust emissions.
High frequency	Trains arrive every 2-10 minutes during peak hours, so passengers rarely check a timetable.
Large passenger capacity	One six-car train can carry 1,000-plus people, replacing hundreds of private car trips.
Dedicated right-of-way	Exclusive tracks prevent delays from traffic lights, level crossings, or freight rail conflicts.
Rapid acceleration	Powerful motors and lightweight cars allow quick station-to-station sprints with short dwell times.
High average speed	Typical service speeds of 30-50 km/h beat surface transit in congested central districts.
Fixed station spacing	Stations sit 800-1,500 metres apart, optimising coverage versus journey speed trade-offs.
Automated signalling	Computer-based train control maintains safe gaps and enables very short headways between trains.
Integrated fare gates	Entry gates and proof-of-payment systems speed boarding and reduce onboard ticket handling.

Common Examples of Metro Systems

London Underground - the world's oldest metro, opened in 1863, now carrying over one billion passengers yearly.
New York City Subway - one of the largest networks globally with 472 stations and 24-hour service on most lines.
Moscow Metro - famed for ornate station architecture and extremely short 90-second peak headways.
Tokyo Metro - a privately operated system moving over seven million riders daily with punctuality measured in seconds.
Paris Métro - a dense 16-line network where no station is more than 500 metres from another.
Hong Kong MTR - a profitable, heavily used system with 99% on-time performance and integrated property development.
Shanghai Metro - the world's longest metro network by route length, exceeding 800 kilometres of track.
Mexico City Metro - a low-fare system running on rubber tyres on some lines to reduce noise and vibration.
Dubai Metro - a fully driverless, automated system with air-conditioned stations in a desert climate.
Copenhagen Metro - a compact, fully automatic system with 24-hour weekend service and no drivers on board.

Advantages and Limitations of Metro Systems

Advantages	Limitations
Moves 30,000-80,000 passengers per hour per direction, far exceeding bus or tram capacity.	Construction costs run billions per kilometre, making new lines prohibitively expensive for many cities.
Operates reliably in all weather because tunnels and viaducts shield trains from rain, snow, and heat.	Fixed routes cannot adapt to changing travel patterns, unlike flexible bus networks.
Reduces road congestion by replacing thousands of private car trips during peak commuting hours.	Deep tunnel stations require long escalator rides and multiple transfers that increase total journey time.
Produces zero tailpipe emissions, cutting urban air pollution and supporting climate targets.	Disruption during construction can last 5-10 years, closing roads and damaging local businesses.
Provides high-frequency service that lets passengers arrive without checking schedules.	Night closures for maintenance strand late-shift workers in cities without 24-hour service.
Offers high safety records with grade separation eliminating most collision and pedestrian risks.	Overcrowding on peak trains creates crush loads, long platform waits, and passenger discomfort.
Increases property values near stations, enabling transit-oriented development and urban density.	Vandalism, graffiti, and fare evasion impose ongoing security and cleaning costs on operators.
Operates with high energy efficiency per passenger-kilometre compared to cars or buses.	Seismic, flooding, and fire risks in underground sections demand costly safety engineering.
Delivers fast journey times with average speeds double those of surface street transit.	Stations spaced far apart leave coverage gaps that force walking or feeder bus connections.
Creates long-term fixed infrastructure that anchors urban growth for decades.	Ageing systems require constant renewal; many networks run trains on signalling and track from the 1970s.

Similarities Between Subway and Metro Systems

Shared Aspect	How Subway and Metro Systems Are Alike
Core Purpose	Both subway and metro systems exist to move large numbers of passengers quickly through urban areas.
Transit Category	Subway and metro systems both fall under the category of heavy rail public transportation.
Primary Fuel	Subway and metro systems both run almost exclusively on electric power rather than diesel.
Passenger Focus	Subway and metro systems both prioritize moving commuters over moving freight or cargo.
Fixed Routes	Subway and metro systems both operate on predetermined, fixed rail lines that never change.
Schedule Structure	Subway and metro systems both run on published, timed schedules with frequent train arrivals.
High Capacity	Subway and metro systems both carry hundreds of passengers per single train consist.
Peak Service	Subway and metro systems both add extra trains during morning and evening rush hours.
Fare Payment	Subway and metro systems both require prepaid tickets, cards, or digital passes before boarding.
Station Stops	Subway and metro systems both use dedicated stations with platforms for safe passenger boarding.
Driver Operation	Subway and metro systems both typically employ trained operators to drive each train.
Track Gauge	Subway and metro systems both use standard gauge tracks of 1,435 millimeters in most cities.
Signaling Need	Subway and metro systems both rely on advanced signaling systems to prevent train collisions.
Safety Systems	Subway and metro systems both install platform doors and emergency brakes for passenger protection.
Accessibility Rules	Subway and metro systems both must provide elevators and ramps for disabled riders.
Public Ownership	Subway and metro systems both are usually owned and operated by municipal or regional governments.
Subsidy Reliance	Subway and metro systems both depend on public subsidies because fares rarely cover costs.
Capital Cost	Subway and metro systems both require billions in upfront investment for tunnels and tracks.
Operating Cost	Subway and metro systems both face high ongoing costs for energy, staff, and maintenance.
Congestion Relief	Subway and metro systems both reduce road traffic by offering a faster alternative to cars.
Emission Reduction	Subway and metro systems both cut urban carbon emissions compared to private automobiles.
Ridership Metrics	Subway and metro systems both measure success by daily passenger trips and load factors.
On-Time Measure	Subway and metro systems both track performance using on-time arrival percentages.
Track Maintenance	Subway and metro systems both require regular rail grinding and track inspection schedules.
Fleet Upkeep	Subway and metro systems both need routine maintenance on brakes, wheels, and doors.
Night Shutdown	Subway and metro systems both close for several hours nightly to perform essential maintenance.
Weather Immunity	Subway and metro systems both operate reliably in rain, snow, and extreme heat.
Expansion Plans	Subway and metro systems both grow through new lines added in phases over decades.
Integration Role	Subway and metro systems both connect with buses and commuter rail at interchange hubs.
Long-Term Asset	Subway and metro systems both serve cities for over a century with proper upkeep.

Subway or Metro Systems: Which Should You Choose?

Choose based on where the tracks run, not train size. Subways run fully underground in dense city cores. Metro systems run on elevated, at-grade, or underground tracks across wider regions. For most riders, the deciding variable is whether you need short downtown hops or regional coverage.

When to Use Subway

Choose Subway when you need rapid transit inside a dense urban core with limited surface space. Use it for short, high-frequency trips under 10 miles, deep tunneling beneath existing buildings, and routes where land acquisition for surface tracks is impossible or cost-prohibitive.

When to Use Metro Systems

Choose Metro Systems when you need regional connectivity beyond the city center across 15-50 mile corridors. Use them for suburban commuter links, airport connections, and interchanges with buses or light rail, where mixed tunneling, elevated viaducts, and surface tracks reduce construction costs.

Common Misconceptions About Subway and Metro Systems

Common Myth	The Reality
A subway always runs completely underground, while a metro always runs above ground.	Subway lines often emerge above ground in suburbs, and metro systems frequently include underground downtown sections.
Metro systems are only found in European cities like Paris or London.	Metro systems operate on every inhabited continent, including major networks in Asia, North America, and South America.
A subway is always older than a metro system in any given city.	Age depends on the specific city; many newer subway lines are younger than established metro networks elsewhere.
The term metro always refers to a heavy rail system with steel wheels on steel rails.	Some metro systems use rubber-tyred trains, like Paris and Montreal, which still operate on dedicated guideways.
Subways are always driverless, but metro systems always require a human operator.	Driverless operation exists in both subways and metros, such as London's Docklands Light Railway and Dubai's Metro.
Metro systems are always larger than subways in terms of track length.	Track length varies widely; some subways, like New York City's, far exceed many metro networks in total route miles.
A subway is a type of train, while a metro is a type of bus or tram.	Both subways and metros are rail-based systems, not buses, and both operate on exclusive rights-of-way.
Subways only exist in the United States, and metros only exist outside the United States.	American cities like San Francisco and Washington, D.C., operate systems commonly called metros, while subways exist globally.
Metro systems always have more stations than subway systems in the same country.	Station counts depend on network design and coverage area, not on the label subway or metro.
A subway train always runs on electricity, but a metro train always runs on diesel fuel.	Both subway and metro trains are almost universally electrically powered, typically via third rail or overhead catenary.
Subways are always public transit, while metros are always privately owned.	Ownership varies; both subways and metros are usually publicly owned, though some operate under private concessions.
Metro systems never share tracks with freight trains, but subways sometimes do.	Both subways and metros typically operate on exclusive tracks, rarely sharing with freight or intercity passenger rail.
A subway is always called a subway, and a metro is always called a metro, everywhere in the world.	Local names vary; London calls its system the Tube, and many cities use terms like MRT, U-Bahn, or underground.
Metro systems always have above-ground stations, while subways always have underground stations only.	Both system types mix underground, at-grade, and elevated stations depending on terrain and urban density.
Subways are always cheaper to ride than metro systems on a per-trip basis.	Fares depend on city policy and distance, not on the system label; some metros are cheaper than some subways.
Metro systems always run 24 hours a day, but subways always close at night.	Only a few networks run overnight, like New York's subway; most metros and subways close for several hours nightly.
A subway is always a single line, while a metro system always has multiple lines.	Both subways and metros can be single lines or integrated networks with multiple routes and interchanges.
Metro systems are always newer than subways because the word metro sounds more modern.	The word metro comes from Paris's Métropolitain in 1904, but many subways predate or postdate that era.
Subways always use third-rail power, and metro systems always use overhead wires.	Power delivery varies by line and city; both subways and metros use either third rail or overhead catenary.
Metro systems always have air conditioning, but older subways never do.	Many older subway fleets have been retrofitted with air conditioning, and some newer metros lack it in mild climates.
A subway is always a rapid transit system, but a metro is always a light rail or tram system.	Both subways and metros are forms of rapid transit, distinct from light rail or streetcars that mix with traffic.
Metro systems always connect to airports, but subways never do.	Many subways connect directly to airports, such as the Chicago 'L' to O'Hare and the Boston subway to Logan.
Subways are always built by digging tunnels, while metros are always built on elevated tracks.	Construction method depends on geology and cost; both subways and metros use tunnels, cuts, and elevated structures.
Metro systems always have platform screen doors, but subways never have them.	Platform screen doors appear in some subways, like Copenhagen and Singapore, and are absent from many metros.
A subway is always a local service, while a metro is always an express service.	Both subways and metros run local and express services, with stopping patterns determined by station spacing and demand.
Metro systems are always named with the word metro in their official title.	Many metro systems use other names, such as the New York City Subway, the London Underground, or the Moscow Metro.
Subways always have turnstiles at every entrance, but metros always use proof-of-payment systems.	Fare collection varies; many metros use turnstiles, and some subways use open platforms with random ticket checks.
Metro systems always have higher ridership than subways because they are more modern.	Ridership depends on city population and network coverage; Tokyo's subway and Moscow's metro both carry billions annually.
A subway is always a single operator, while a metro system always has multiple competing operators.	Both subways and metros usually have a single public operator per city, though some regions integrate multiple agencies.
Metro systems always use automated announcements, while subways always rely on manual conductor announcements.	Automation of announcements varies by line and age; many subways use automated systems, and some metros still use manual calls.

Conclusion

Difference Between Subway and Metro Systems comes down to branding and scope. Subway often describes a single city's underground rail. Metro systems can include above-ground lines and multiple operators. Choose subway for local, underground transit. Choose metro for broader, regional networks. Both move people efficiently.

FAQs on Difference Between Subway and Metro Systems

What is the main difference between a subway and a metro system?: The main difference is that a subway is a specific type of metro system that runs entirely underground, whereas a metro system is a broader term for any urban rapid transit rail network that can run underground, at grade, or on elevated tracks.
Are subway and metro systems the same thing?: No, they are not the same thing because a subway is always a metro, but a metro is not always a subway, as metro networks often include above-ground and elevated sections in addition to underground tunnels.
Which is better for a city, a subway or a metro system?: Neither is inherently better because the choice depends on a city's geography, budget, and density, with subways offering land savings in crowded downtowns while metros with surface lines cost significantly less per mile to build.
Is it more expensive to build a subway than a metro system?: Yes, building a subway is typically more expensive because tunneling costs can reach hundreds of millions of dollars per mile, whereas at-grade metro tracks cost a fraction of that amount to construct.
Are subways safer than metro systems?: Subways are generally safer than surface-level metro systems because underground tracks are fully segregated from road traffic, pedestrians, and weather hazards, eliminating the risk of grade-crossing collisions and falling debris.
Can a metro system run entirely underground like a subway?: Yes, a metro system can run entirely underground, and when it does, it is correctly classified as a subway, such as the London Underground or the New York City Subway.
What is a common beginner mistake when using subway and metro terms?: A common beginner mistake is assuming the terms are interchangeable globally, when in reality a subway specifically refers to underground rail while metro is the generic category, and many cities use the words based on local convention rather than technical accuracy.
Can you use a subway ticket to ride a metro system?: Yes, you can use a subway ticket to ride a metro system because a subway is a component of the larger metro network, so the same fare and ticket are valid for all lines within that unified system.
Why do some cities call their underground rail a metro instead of a subway?: Some cities call their underground rail a metro instead of a subway because the term metro is a shortened form of metropolitan railway that gained popularity in Paris and is now the standard international name for urban rapid transit networks.
Can I switch from riding a subway to a metro system on the same trip?: Yes, you can switch from riding a subway to a metro system on the same trip because they are part of one integrated network, and transfers between underground and above-ground sections are common and usually free within the same fare zone.