Mr. Frederson owns all of these foundries and factories. During a frivolous romp through his gardens and fountains, Frederson's son, Freder, spots Maria, the daughter of one of the workers. She is playing with a group of children, and he's smitten with her fresh-faced innocence. Sneaking a peek at the condition of the workers in the underground, Freder is shocked by the multitude of faceless bodies and the dark, airless atmosphere.
When Mr. Frederson overhears Maria comparing the factory workers to the slaves who built the Tower of Babel, he decides to have his chief scientist build a robot version of her. His plan: to have the robot incite a rebellion, thereby providing a pretext for him to replace his inefficient human workers. Maria's transformation into a robot is one of the most spectacular effects ever put on film. The robot Maria is a sensual, frisky, lusty, flirtatious preacher of the proletarian message.
When the workers revolt, young Freder awakens the real Maria, who turns him into a mediator between the workers and his father, the master of Metropolis. And in the end, the guy gets the girl.