The Iron Man from the 1970 song by Black Sabbath is an unnamed man of good intent who built a time machine and traveled to the future, only to glimpse an apocalypse in progress.
Immediately, he began to make the trip back to save the world from this terror. But somehow, the return trip warped his body into a hulking metal form, in which he was unable to communicate his dire warning, and was attacked instead. Enraged, he began tearing civilization apart, leading to himself being the cause of the apocalypse he tried to warn people of. The story is a simple but savage time loop, driven home by the band's primal driving chords and beats.
This version is obviously not the heroic Marvel character, but has become associated with him, especially since the song's use in the Iron Man feature films, to which Robert Downey, Jr. payed homage to by wearing a Black Sabbath T-Shirt during the 2012 Avengers feature film.