Are they robots? Perhaps not made of metal and circuits, but they're definitely artificial, as in designed, engineered, and manufactured. In fact, going into the definition of "robot," we find it means "a machine made to look like a human, that can perform various tasks." Pretty sure Rutger Hauer performed various tasks in this film, while looking human.
I've gone over this film before at length, but we must bring it up again. Rutger "Roy" Hauer fights against a society that's deemed him expendable and insignificant, only to end up realizing they're right and achieving self-awareness in death. With no way to extend his shelf-life and his creator being a crippling disappointment, Roy transcends his origin and truly knows what it is to be human. Roy learns you can't live forever, sometimes as you grow up the halo you place on your parents loses its shine, and all that truly matters is your actions and how you are remembered. He ends his existence saving Harrison "Indiana" Ford's life. Does that make him more human? Was Harrison a synthetic himself? Depends on what version you watch.
This movie pretty much has the same premise as E.T.: A being from space lands on Earth and becomes friends with a young boy. The boy teaches him about customs and even introduces him to Superman comics. Director Brad Bird definitely loves superheroes because his next film was Pixar's The Incredibles.
In this scene, a rocket is headed to the little boy's town to destroy the Iron Giant. The whole film has a 1950s almost-art deco/cold war theme going on, and someone was a little trigger happy. The little boy Hogarth explains to his robot friend that when the missile hits, everyone will die. The Giant tells Hogarth to stay and not follow him, then launches himself into space to intercept the missile. The most powerful moment is when Hogarth tells the Giant that he loves him and when the Giant sacrifices himself. He closes his eyes and says: "Superman."