Actors like to discuss the importance of pushing themselves, of venturing into unfamiliar and sometimes scary emotional terrain. When they explore such challenges and pull it off, they're congratulated for their courage and commitment.

So, let us salute Tom Cruise for his work in Rock of Ages. Far more than a throwaway cameo, the megastar's turn as Stacee Jaxx, a tattooed rock god in the heavy-metal firmament, is full-on and fearless. A strutting stallion, whipping his long locks across his rippling torso, Jaxx takes to the stage with aplomb - and then to the dressing room, with as many groupies as his roadies can muster.

Whether Cruise's performance is served up with irony or without, however, is another question. And that's a question that pops up frequently as you watch Rock of Ages - a jukebox musical that's astonishingly cornball one minute, winkingly sardonic the next.

Deploying an arsenal of anthemic '80s hits ("Don't Stop Believin'," "I Want to Know What Love Is," "Hit Me with Your Best Shot," and plenty more) and the hairdos that go with them, Rock of Ages begins on a bus: Sherrie Christian (Julianne Hough) is a wide-eyed Oklahoman determined to make it big as a singer in Hollywood.

Of course, no sooner has she set foot on Sunset Boulevard than she's ringed by hookers and thugs - but don't worry, the denizens of the night know how to break into a song-and-dance routine, too.

Hough, who starred in the recent remake of Footloose, is ready for anything choreographer Mia Michaels throws at her - even a gymnastic pole-dance number, which she gyrates her way through at a gentlemen's club run by Mary J. Blige. Sherrie's dreams of fame aren't working out, and she's gone from cocktail waitress in a rock club to fending off gropers in a strip joint.

Sherrie's love interest and fellow music-biz aspirant is Drew Boley (Diego Boneta), a scrappy chap who works for Dennis Dupree, the bloodshot proprietor of the legendary Bourbon Room. Alec Baldwin - with long hair, stubble, and a moony look in his eyes whenever his house manager, Lonny (Russell Brand), walks in - is Dupree. There's little doubt that Baldwin and Brand are playing things for laughs - but the way these guys carry on, it's almost as if they're in their own movie, or a Saturday Night Live sketch.

Catherine Zeta-Jones is an antirock crusader with a skeleton or two in her closet; Paul Giamatti is Jaxx's smarmy manager; and Malin Akerman is an intrepid Rolling Stone reporter, determined to get the what-makes-him-tick interview out of Jaxx. That these two end up locking lips (and more) is only inevitable.

Rock of Ages began life as a stage show, and maybe the rock-and-roll stereotypes played better in person than they do on the big screen. But if you have a soft spot for the glam and pomp of Journey, Bon Jovi, Pat Benatar, Twisted Sister, Steve Perry, and Styx, there are worse ways to spend a couple of hours than with this odd assortment of courageous thespians bringin' on the heartbreak, and feelin' the noize.