'Iron Man' opened in theaters across the US on this day in 2008. The movie was the first film in Phase One of the hugely successful Marvel Cinematic Universe and went on to become the eight-highest grossing film of 2008, earning more than $585 million at the worldwide box office. It's success led to two sequels: 'Iron Man 2' (2010) and 'Iron Man 3' (2013).