Metro or subway systems are common in large cities and metropolitan areas. They run underground or on elevated tracks and are designed for fast, high-capacity urban travel. These systems are usually the quickest way to move across busy cities. Costs are generally moderate and cheaper than taxis or ride-sharing services. Fares may be based on distance, zones, or a flat rate per ride. Payment options often include reusable smart cards, single-journey tickets, mobile apps, and contactless bank cards. Many systems also offer unlimited daily, weekly, or monthly passes that provide better value for frequent users. Metro stations usually have automated ticket machines with multiple language options, making them traveler-friendly. Clear signage, maps, and color-coded lines help with navigation. Although metros are efficient, they can be crowded during rush hours. Security checks and fare inspections are common in some countries. Overall, metro systems provide speed, reliability, and convenience for daily commuting and sightseeing.