Metro depicts the life of four people, a barman, a lottery-ticket seller, a security man and a cleaning lady, who work in the Barcelona metro, a maze of tunnels and passages which constitute a meeting place for over a million passengers per day, and a lively social-life. Coffee shops, gambling machines and kiosks take the form of a dynamic, living city which is a dark copy of the city above. Through the portrait of this underground microcosm, the film attempts to draw some conclusions on the above-ground Barcelona.