On a slow night, why not watch an enjoyable, well-made big-budget superhero movie? You don’t have to have seen either of the other Iron Man films to get into this one, especially with the irresistibly charming central performance by Robert Downey, Jr. as Tony Stark, a.k.a. Iron Man. But watch, too, for Don Cheadle as another metal-suited hero, who matches Stark punch for punch – and also matches Downey quip for quip.