What does Black Sabbath song have to do with Iron Man?

Josh Glenn says:

In this new Brainiac item I crack the lowbrow literary mystery, "What — if anything — does the awesome and influential Black Sabbath song 'Iron Man' have to do with the Marvel superhero? Or the Ted Hughes kiddie book, for that matter?" Having puzzled out the solution to this question, over which metalheads continue to wrangle nearly 40 years later, I offer a theory about what the 1970 antiwar song has to teach us today. Just in time for the new "Iron Man" movie!