Diamonds be damned — an iron-clad Robert Downey Jr. makes for a better best friend any day. Once again, Downey suits up as charming asshat Tony Stark — spouting off the token tongue-in-cheekers rampant in the comic-turned-film’s first installment.

In “Iron Man 2,” Stark is caught in the middle of a legal clusterfuck, fast-talking his way out of handing the Ironman suit over to a concerned U.S. government working in conjunction with opportunistic sleazeball Justin Hammer (Sam Rockwell). Stark boldly claims that no one could possibly stumble upon similar technology within the decade. How wrong he is.

Just days later, muscle-bound Russian Ivan Vanko (an electrifying Mickey Rourke) whips the superhero around in a suit made with identical technology. The rivalry comes to a head at Stark’s Expo, culminating in a metal-crunching standoff that makes for one hell of a shrapnel show.

It takes a special type of swagger to turn iron to gold — and Downey’s performance as the iron-hearted Stark does just that. Charming and snarky, Downey is a winner alongside Paltrow, exchanging high-speed banter and throwing self-indulgent parties at which he gets smashed and dances like a baffoon. Downey plays up Stark’s fallibility, breathing life into a hero so frequently described as godlike.

Antagonists Rourke and Rockwell never fade from view, either. Rourke growls in good Russian — spitting blood, peppered with metal — and Rockwell verbally bombards anyone unfortunate enough to fall into his greasy web of egomania. Even store-mannequin Scarlett Johansson is surprisingly well -placed, deadpanning throughout as taciturn, bra-flashing badass Natalie Rushman.

Bolstering the cast, director Jon Favreau keeps the special-effects team to the grindstone as well, churning out streaming lighting blasts and enough gasoline-packed explosions to power Stark’s Audi. The effects are engaging enough to capture even the girliest of filmgoers, filling the void left by the nauseating plotline of metal-mashing giant “Transformers 2.”

But “Iron Man 2” has its sharp edges. Favreau makes little effort to forge any new ground in the way of unexpected twists; Vanko’s thirst for vengeance on his family’s behalf is exhaustively expected. Though the flimsy storyline is lacking the kind of weight delivered by “The Dark Knight,” the film’s colossal effort in all other departments nearly irons out its shortcomings. And for those hankering for more hot iron-on-man action, be on watch for the clip that rolls after closing credits — looks like the next Marvel film is already being hammered out.