The central twist of Metropolis is the kidnapping of the virtuous Maria and her replacement by a robotic doppelgänger, the Machine-Man. Joh Fredersen commissions this creation to discredit the real Maria and sow confusion among the workers, aiming to prevent a rebellion. However, the inventor Rotwang, driven by a personal vendetta against Fredersen, secretly programs the robot not to quell the workers, but to incite them into a destructive frenzy that will destroy the entire city. The robot, as a hyper-sexualized and chaotic version of Maria, first captivates the sons of the elite with a decadent, sinful dance, symbolizing the moral corruption of the upper class. It then delivers fiery speeches to the workers, turning Maria's message of peace into a call for total annihilation of the machines.
This manipulation leads to the film's climax: the workers, in a revolutionary fervor, destroy the Heart Machine, the central generator of the city. They celebrate their victory, only to realize with horror that its destruction has caused the reservoirs to overflow, flooding their underground city and trapping their children. This reveals the hidden meaning that a blind, rage-fueled revolution is ultimately self-destructive. As the real Maria, who has escaped, helps Freder rescue the children, the workers capture the false Maria and burn her at the stake. The flames melt away her artificial flesh, revealing the metallic skeleton of the robot underneath, exposing the deception to the horrified mob. The film concludes with Rotwang, now completely insane, chasing the real Maria to the roof of a cathedral. Freder pursues him, and after a struggle, Rotwang falls to his death. This entire sequence sets the stage for the final, symbolic reconciliation: Freder, having saved both the workers' children and Maria, acts as the "heart" and joins the hands of his chastened father (the "head") and the lead worker, Grot (the "hands").