Could there be a more American superhero than Iron Man? He’s not just a crime fighter, he’s a weapons system. This adaptation of the long-running Marvel Comics series, directed by Jon Favreau, is steeped in machine tooling and digital information screens, with men doing battle while bolted inside gigantic high-tech metal contraptions. Robert Downey Jr. gives a nicely sardonic performance as Tony Stark, a rich playboy and the brilliant heir to his father’s weapons manufacturing dynasty. The movie is so clever and smoothly paced that it’s easy to overlook the odious story line, in which Stark suffers an attack of conscience during a disastrous trip to Afghanistan, realizes his corporation is supplying Taliban-like bad guys, and goes after them in his iron death suit. Of course coming back to destroy his own stuff makes him the perfect metaphor for the U.S., an irony Favreau ignores. With Jeff Bridges, Gwyneth Paltrow, and Terrence Howard. PG-13, 126 min.