Rotwang is a brilliant scientist and inventor, whose greatest achievement is the creation of a robot made in the form of a woman (the Maschinenmensch, or Machine-Person). Originally, he intends to make a replacement for his lost love, Hel. Hel was a beautiful woman who eventually chose Joh Fredersen, master of the city and Rotwang's rival, instead of him. She later died while giving birth to Fredersen's son, Freder. Rotwang instead uses the robot to get revenge against Fredersen and Freder, while pretending that he is using the robot for Fredersen's benefit, and under Fredersen's instructions. Instead of making it into a replica of Hel, he abducts Maria, a saintly woman who has a following among the oppressed workers. He creates a promiscuous and violent "false Maria" who incites rebellion among the workers and destructive lust among the wealthy classes. During the ensuing citywide riots and power blackout, Rotwang goes mad and chases the real Maria through Metropolis, believing her to be Hel. Freder pursues him to the roof of the city's cathedral, where the two fight and Rotwang falls to his death.

Rotwang lives in a strange old house in the middle of Metropolis; its rough exterior design contrasts sharply with the futuristic elegance of the city. In its basement is a trap door that leads down into a network of underground catacombs, where Rotwang and Fredersen eavesdrop on a secret meeting of the workers and Maria, their spiritual counselor. He lost a hand while developing the Machine-Person and now wears a fully functioning metal prosthesis in its place.