John Henry Irons is a weapons designer for the United States military. When his project to create weapons that harmlessly neutralize soldiers is eradicated, he resigns in disgust. When he sees criminal gangs are using the weapons that he helped manufacture on the street, he uses his resources and his Uncle Joe's equipment in his junkyard to fight back against the man who's been selling them to those gangs: Nathaniel Burke. In order to do so he uses the resources that are available to him to forge himself a suit of armor and the weaponry necessary to carry out his war on crime.
During the scene at the railroad where John Henry Irons chases after a thug, a broken down fence has graffiti that resembles the written alien language from Alien Nation. Kenneth Johnson, who directed this movie, also directed several Alien Nation TV movies.
Shaquille O'Neal is alleged to have done all of his own stunts since the producers were unable to find a 7'1" stunt double for him. This is, however, disputed.
In the Steel comic book, John Henry Irons was directly inspired by Superman when Superman saved his life just during the Death of Superman story arc (both literally and metaphorically). Since then, John Henry Irons sports Superman's shield as a homage to the Man of tomorrow. In the movie, the existence of Superman is almost completely avoided. However, John Henry Irons is still related to Superman (albeit more subtly) via his tattoo (a genuine tattoo that Shaquille O'Neal sports as he's an avid Superman fan), and a single line said to John by his uncle saying "You ain't Superman!"* Susan Sparks is based on the DC Comics character Oracle.