Iron Man (Robert Downey Jr. plus a heap of hardware) is quite literally falling apart in "Iron Man 2." Tony Stark, the man in the glossy, scowling mask, is being eaten away from the inside by toxic fuel cells in his artificial heart. The genius military-industrialist's one-man monopoly on peacekeeping is under attack from U.S. Sen. Stern (smarmy Garry Shandling) and Justin Hammer, a jealous rival industrialist (Sam Rockwell, a painfully unhip Michael Dell to Downey's supercool Steve Jobs).

Worse yet, Ivan Vanko (Mickey Rourke), a Russian antihero wielding electro-laser whips, wants to slash Iron Man to smithereens. His friendship with Lt. Col. James Rhodes (Don Cheadle) is on the rocks. Understandably, Stark's alcohol intake is spiking and his self-control is slipping.

The story goes to pieces, as well. Screenwriter Justin Theroux ("Tropic Thunder") fashioned a hopscotch plot that is little more than an excuse to have the leading characters swing their big metallic fists. The aimlessness of "Iron Man 2" runs deep. There's no world-in-peril scenario unfolding here; what's at stake is the fate of Stark's military contracts. New characters accumulate with scant justification; Scarlett Johansson co-stars largely for the sake of a single acrobatic fight scene. There are a couple of in-jokes foreshadowing future appearances by the Marvel superheroes Captain America and Thor, and plenty of Downey wisecracks that seem more calculated to tickle the audience than advance the story.

Comic-book extravaganzas don't have to be this hectic and half-baked. Watch this one thinking of Christopher Nolan's "Batman" films, Paul Verhoeven's "Robocop," "Richard Donner's "Superman" and Sam Raimi's first two "Spider-Man" offerings. Then think of the opportunity director Jon Favreau has missed. This cluttered, awkward blockbuster is held together by safety pins and movie-star charisma.

Downey plays the smug superhero with his usual flair. Stark is a self-centered rich kid who revels in the attention that comes with saving the world. He's fighting for truth, justice and the American way, but he's doing it with an ironic smirk. Downey's Stark is a highly combustible mix of ego and integrity with a few thorny Oedipal issues tossed in for good measure.

One of the film's pleasures is its time-capsule views of Tony's late father Howard (John Slattery) in a promotional film. As he sets forth his plans for a utopian city of the future, like Walt Disney unveiling Tomorrowland, we get a glimpse of the deeply mixed emotions our hero still feels toward the man. Tony earned his bullheaded antiauthoritarian streak the hard way.

What saves the film is not profound character insights but an amiable sort of momentum. As the tale zips along it's too much effort to be irritated, so you end up being entertained. Who cares if the story doesn't track particularly well? There's so much to look at, so many moments of pure geek pleasure. The pace of the battle scenes is fast and flamboyant, the robot suits are sleek and agile, the airborne action is filmed from zany angles.

There's a nervous sense of peril in the scene at the Monte Carlo Grand Prix where Vanko attacks Stark as he drives a Formula 1 racer. Vanko's flailing whips snap Stark's car like a saltine, and the stunned billionaire crawls from the wreckage amid autos colliding, flipping sky high and exploding spectacularly. For once his cocky air is gone. Vanko lumbers toward his prey at a sure, unhurried pace, savoring Stark's shock, grinning at his helplessness.

Now that's how a villain does it. It's hard not to smile and enjoy as well.

Colin Covert • 612-673-7186