Unlike far too many comic book movies (and there are far too many comic book movies), "Iron Man 2" neither takes itself too seriously nor overplays its potential for humor. Jon Favreau, who directed, may deserve some of the credit for the movie's many laughs; he mostly specializes in comedy, perhaps a good preparation for adapting to the big screen a source aimed at juveniles.

The picture opens its comic possibilities with the spectacular appearance of its hero, the colossally narcissistic billionaire Tony Stark (Robert Downey, Jr.), a sort of Donald Trump on steroids, at his own version of the World's Fair, once again in Flushing Meadows, New York. He emerges from his high-tech armor, preening and prancing in a circle of underdressed showgirls, while a crowd of thousands cheers in adoration. Stark informs the throng about just how wonderful he is, and promises to continue his heroic work fighting evil all over the globe; he later announces to a hostile congressional committee that he has successfully privatized world peace.

As everyone expects, Stark's hubris guarantees some major difficulties in the near future, one from a competitor, Justin Hammer (Sam Rockwell), the other from a Russian inventor, Ivan Vanko (Mickey Rourke), who designs a special suit of his own. In the interests of free-market capitalism, Hammer employs Vanko, who nurses a grudge against Stark, to defeat the billionaire and win enormous government contracts for his own armored fighting machines.

The competition between Stark and Hammer naturally proceeds to a series of violent confrontations between a couple lumbering mechanical giants. Stark's sleek suit, equipped with a wide array of gadgets, contrasts sharply with the Russian's crude harness and crackling electronic whips and lariats, but the Russian proves a worthy opponent, with enough genius and malevolence to match the Iron Man. In another unusual difference, Rourke constantly tinkers with crude spare parts like some amateur mechanic, while his counterpart gracefully conducts an orchestra of holographic computer images and robot assistants; as usual, the sheer process proves more compelling than the results.

Aside from the punctuation of frequent clashes between various mechanical behemoths, with the usual collection of fireworks and the really serious demolition that unimaginatively drive its genre, whatever real success "Iron Man 2" achieves grows out of its characters and its sense of fun. Maimed like the gods and heroes of myth, the superhero Tony Stark suffers his own point of vulnerability, a rapidly increasing toxicity from the device implanted in his chest that paradoxically keeps him alive and battling; his awareness of his mortality explains some of his mercurial behavior when he steps out of his fancy suit and impersonates himself instead of his formerly secret identity.

Although the script provides very little dialogue for Mickey Rourke - and that delivered in a heavy Russian accent - bulging with muscles left over from "The Wrestler," wallpapered with myriads of indecipherable tattoos, and his smile glittering with the best Russian stainless steel, he fills up a certain grotesque space on the screen. Sam Rockwell steals most of his scenes with a barrage of sycophantic dialogue and a kind of charming amorality in his attempts to sell firepower to the military, persuade Vanko to design a killer robot, and of course, to defeat Tony Stark.

Most surprising, in the midst of the stunts, explosions, and pyrotechnics, the script displays a considerable wit. The frequent arguments between Tony Stark and his assistant Pepper Potts (Gwyneth Paltrow) resemble the rapid-fire, back-and-forth banter of 1930's stichomythia; in fact, the usually insipid Paltrow, lovely, angular, and uncommonly elegant, now and then resembles those smart, funny, edgy women of the great Hollywood comedies. Her verbal sparring with Downey recalls the electric sparkle of such pairings as Katharine Hepburn and Spencer Tracy, Lauren Bacall and Humphrey Bogart, Rosalind Russell and Cary Grant.

As for Robert Downey, who now apparently moves seamlessly from hit to hit, he maintains something of the casual, offhand delivery of his recent success in "Sherlock Holmes." Though he hardly extends himself, he displays a genuine gift for understated, ironic drollery, nicely suited for the movies if not terribly useful in the comic books. He seems good enough to wear that Iron Man suit for a long time to come.