Plot
The film is set in the massive, sprawling futuristic mega-city Metropolis, whose society is divided into two classes: one of planners and management, who live high above the Earth in luxurious skyscrapers, and one of workers, who live and toil underground. The city was founded, built, and is run by the autocratic John Fredersen.
Like all the other sons of the managers of Metropolis, Freder, Fredersen's son, lives a life of luxury in the theatres and stadiums of the skyscraper buildings. One day, as he is playing in the Eternal Gardens, he notices that a beautiful girl has appeared with many children of the workers. She is quickly shooed away, but Freder becomes infatuated with her and follows her down to the worker's underworld. There, he experiences firsthand the horrors of the worker's life, and is disgusted when he sees an enormous machine, known as the M-Machine, violently explode and kill dozens of workers. In the smoke, Freder envisions the M-Machine as Moloch, a monstrous deity to which the hapless workers are sacrificed.
Disgusted, Freder returns to the New Tower of Babel, a massive skyscraper owned by his father. There, he confronts his father and starts crying about the accident at the M-Machine, but Fredersen is more annoyed about hearing about the accident from his son and not from his clerk Joseph. Grot, foreman of the Heart Machine, informs him of papers resembling plans or maps, which have been found in the dead workers' pockets. Fredersen fires Joseph and also charges his spy, a slim man, to keep an eye on his son.
Freder keeps Joseph from committing suicide and hires him to help with his quest to help the workers. Freder descends to the worker's underworld again and meets someone named Georgy 11811, who works a machine that directs electrical power to the enormous series of elevators in the New Tower of Babel. Freder persuades Georgy to exchange clothes with him, go to Freder's apartment, and let Freder work at the machine. Georgy, who finds large blocks of money in the pocket of Freder's clothing, goes to Yoshiwara, the city's red-light district. While Georgy enjoys a night of wild and passionate partying, Freder works at the machine until he becomes delirious, having visions of being crucified to the factory clock.
Fredersen, wondering about the papers found, decides to consult the scientist Rotwang, his old collaborator, who lives in an old house contained in the lower levels of the city. The two were friends but then became rivals over the love of a woman. Rotwang loved a girl named Hel but when he introduced her to his friend, Hel abandoned him to marry the much more wealthy and powerful Fredersen. Hel died giving birth to Freder, leaving both Rotwang and Fredersen heartbroken and loathing themselves and each other. While Fredersen has moved on, the scientist's love for Hel and his hatred to Fredersen remain as strong as ever. Rotwang introduces Fredersen to a machine-man he has constructed and which he intends to give the image of Hel and marry her.
When Fredersen seeks Rotwang's counsel about the papers, Rotwang explains that they are maps to the 2,000-year old catacombs that are deep under the lowest levels of the worker's city. The two decide to go exploring the catacombs and climb down a tunnel. From a gap in the rocks, they observe the workers gathering in a cathedral hewn from the rock. There, the beautiful Maria appears and begins preaching to the workers (among them the disguised Freder) about the Tower of Babel and about how they must wait for the coming Mediator and also that the heart must be mediator between the mind (the planners) and the hands (the workers).
Brigitte Helm as Maria, held prisoner by Rotwang
At the end of the sermon, Fredersen turns away and begins thinking, while Rotwang notices one worker staying behind, and talking to Maria, revealing himself as Fredersen's son and telling her that he realizes that he is the Mediator that they have been waiting for. Fredersen instructs Rotwang to give the machine-man the image of Maria to then sow distrust between her and the workers. Rotwang agrees but has ulterior motives, intending to use the machine-man to ruin Fredersen's life. While Fredersen returns to his offices, Rotwang captures Maria and imprisons her in his house. There, he performs experiments on her and transforms the machine-man to look exactly like Maria. He then instructs it to, by any means that does not hurt Rotwang or herself, to destroy Fredersen's city and murder his son.
Rotwang demonstrates the machine-man's abilities to Fredersen by dressing it up as an erotic dancer at the Yoshiwara, where it drives the sons of the owners into homicidal fits of sexual jealousy. The body count is enormous; meanwhile, the machine-man also visits the workers city and encourages the workers to rebel. They storm out of the workers city in a full-scale riot and destroy the Heart Machine, the city's power generator. This results in a complete hydraulic breakdown. The city's reservoirs overflow and flood the worker's city to the brim, and seemingly drown the children of the workers. In fact, the children were saved by the real Maria and Freder in a heroic rescue.
When the workers realize what they have done, and that they have killed their children, they blame Maria. Under Grot's leadership, they dash to the upper city and run through the streets, chasing the real Maria, rather than the machine-man. They run into Yoshiwara and meet the owners' sons, led by the machine-man. In the ensuing confusion, the machine-man is tied to a stake and is burned to death.
Meanwhile, the real Maria is chased by Rotwang, who takes her for the machine-man and now wants to give her the likeness of Hel after all. In a climactic scene, Fredersen watches in horror as Freder and Rotwang fight on the cathedral's roof. Rotwang falls to his death, and Freder and Maria return to the street and unite Fredersen and Grot, thus ending the brutality of the city.
