Writing and recording
Upon hearing the main guitar riff for the first time, vocalist Ozzy Osbourne remarked that it sounded "like a big iron bloke walking about". The title became "Iron Man", with Geezer Butler writing the lyrics around the title. Ozzy Osbourne sang behind a metal fan to get the sound effect in its first line, 'I am Iron Man!'. Despite the title, the song has no connection to the Marvel Comics character of the same name.
The lyrics tell the story of a man who time travels into the future, and sees the apocalypse. In the process of returning to the present, he is turned into steel by a magnetic storm. He is rendered mute, unable verbally to warn people of his vision of impending destruction. His attempts to communicate are ignored and mocked. This causes Iron Man to become furious, and drives his revenge on mankind, causing the apocalypse seen in his vision, alluding to Joseph Stalin (whose name literally means "Man of Steel").