In the movie, Atom is a smaller robot originally created just for sparring. He doesn't have a real face, but a welding scar resembles a sort of nose and mouth, setting off the piercing blue eyes and adding a sense of humanity to the machine. Atom can shadow the movements of humans, and so he has an advantage in obtaining the skills needed to become a great boxer. He is also extremely resilient. Max believes in Atom from the start, and he is determined to make him a great fighter. Is Atom just a programmed machine, or is there more intelligence than meets the eye? That is for the audience to decide.
Real Steel was made using performance capture animation to create the robots. Real boxers, coached by Sugar Ray Leonard, performed the scenes in performance capture suits, and then their performances were tied to the CG robots and inserted into the film. Some scenes, however -- those which needed a bot to interact with or were too difficult to shoot using CGI -- involved life-size animatronic versions of the bots built for the movie to look exactly like and provide a model for their CG counterparts.