Every era gets the beefed-up action-film demigod it deserves. Twenty years ago, Arnold Schwarzenegger was the right hulk at the right time. His brusque Teutonic accent, like his engorged physique, was always a semijoke, but in the formative years of the Reagan age, his outsize eccentricity was somehow goofy-cool. He seemed to speak to the notion that pure aggressive will, for America at large, remained a somewhat foreign concept.
It may be less foreign now. In an age of ongoing military engagement, the ability to assert our will comes a lot more naturally than it once did, and that's part of the appeal of The Rock: He makes invincible displays of strength look easy and charming. Parody, of course, is built into his act as a professional wrestler, and as he has proved in two appearances on ''Saturday Night Live,'' he's a gracious, sly-dog comedian with a knack for self-mockery that makes Arnold's look practically medieval in its obviousness.
As Mathayus, the ancient desert assassin of The Scorpion King, The Rock commands the screen as naturally as he does the ring; he's like Arnold with a fresh coat of paint, and a fresh personality, too. In the film's prologue, he shoots a bow and arrow so hard that the pierced victim goes spinning through the air. Then, in a very calm close-up, he says ''Boo!,'' all to let you know that he's perfectly jovial about the lethal tasks at hand. The camera likes The Rock's face, and that's because it's an interesting face -- at once exotic and square-jawed suburban, with small daggers for sideburns, even smaller ones for eyebrows, and shocking white eyes that pop out with the incongruous ferocity of a hypnotist's. He looks like a cross between Rob Schneider and Tony Robbins, and it's that small man/big man counterpoint that makes him such an approachable, humanistic giant.
The Rock may be the new face of Hollywood action, but ''The Scorpion King'' isn't exactly a lightning vehicle. Executive-produced by WWF mastermind Vince McMahon (a frightening thought), and directed by Chuck Russell, who made what is arguably the logiest Schwarzenegger movie ever (''Eraser''), ''The Scorpion King'' is The Rock's version of ''Conan the Barbarian'' -- a clunky, primitive platform for a star who has yet to get in full touch with his inner Terminator.
The picture is being marketed as a prequel to ''The Mummy'' and ''The Mummy Returns,'' and technically speaking, that's exactly what it is. But fans of that series, with its armies of digital goblins that never look too threatening because they appear to be made entirely of fairy-dust pixels, may miss the sensation of spending two hours living inside a videogame. With the exception of one brief sequence, in which The Rock, buried up to his neck in sand, has to with-stand an onslaught of creepy-crawlies, ''The Scorpion King'' isn't a techie-blowout visual-effects party. It's crude and prosaic, a storming-the-cardboard-castle potboiler with reasonably vigorous sword fights served up every 15 minutes or so, like commercials.
In place of the hieroglyphic Indy Jones Lite mumbo jumbo that Brendan Fraser and Co. had so much fun whipping through, we get a lumbering plot in which Mathayus, known as the Akkadian (he's the last of a breed), is hired to do away with Memnon (Steven Brand), a fascist conqueror in a fancy Mohawk who seems no more threatening than a surly British concert promoter. With his longhaired heavy-metal gladiator stylings, The Rock may have copped his look from Tina Turner's henchman in ''Mad Max Beyond Thunderdome,'' but in ''The Scorpion King,'' you wish he were surrounded by a comparable level of decadent excitement. Mathayus teams up with one of those scruffy-pest sidekicks (Grant Heslov), who speaks in a nameless foreign accent as he delivers lines like ''They've got the city sealed up tighter than a crab's buttocks!''
In addition, he absconds with the Sorceress, who has the ability to foresee the outcome of any battle -- a good idea that the movie doesn't do enough with. As played by Kelly Hu, the Sorceress isn't much more than a midriff and a breathy monotone.
As a filmmaker, Chuck Russell has a way of cutting between forceful establishing shots -- of a mountain, a desert, a castle -- and close-ups so stagy that they border on invitations to revive ''Mystery Science Theater 3000.'' ''The Scorpion King'' as a whole, however, isn't incompetent; it's just plodding and obvious. If anything holds it together, it's The Rock's ironic ability to tread lightly, which the movie is neither fast nor inventive enough to recognize as different from the spirit of Arnold. With Schwarzenegger, you feel the heavy labor that goes into crushing each foe. The Rock is more like a colossus for the age of special ops: He looks all too happy to kill without bruising.