ABBA songs are, of course, evil in musical form.

Just try getting "Dancing Queen" out of your head once it's burrowed its way in there. "Waterloo," too, is especially pesky. But "Mamma Mia" might be the most tenacious tune in the 1970s Swedish pop group's canon.

The insanely catchy hit inspired a hugely successful Broadway musical a decade ago and now is the basis for a big, summer movie. "Mamma Mia!" is a massive mess, but it's fun -- exuberantly goofy, sloppily crafted fun, especially if you're not in the mood for thinking too hard.

Phyllida Lloyd, who directed the stage production, makes her filmmaking debut here, and her years of directing opera and theater don't seem to transfer well to the big screen. Some shots look totally green-screen fake; sometimes shadows obscure the actors and at other times the lighting is so flat and bright, it makes everything look like some low-budget effort airing on PBS. And the excessive use of zooms was probably unnecessary, unless Lloyd was aiming for a kitschy 1970s vibe -- a movie version of an ABBA video, perhaps (although the story is set in 1999).

If "Mamma Mia!" works on any level at all, it's through the sheer radiance of Meryl Streep, clearly having a blast letting loose as its star, the former rocker chick Donna. Watching the woman who is considered the greatest actress of our time writhing around in overalls on top of a barn or belting out numbers in a sparkly, spandex jumpsuit and platform boots can indeed be a hoot.

Streep was a fan of the Broadway show, and her passion and enthusiasm explode on screen. She can indeed sing, a talent that's been on display in bits and pieces in previous movies, most recently Robert Altman's "A Prairie Home Companion." (The Hollywood Foreign Press Association, which loves Streep, may as well go ahead and give her the Golden Globe for this performance now. Her showy rendition of the ballad "The Winner Takes It All" ought to seal it for her.)

Amanda Seyfried ("Mean Girls," "Big Love") is also solid as Donna's daughter, Sophie, who is getting married on a Greek island and invites three of Donna's former flames to determine which one is Sophie's father. Christine Baranski and Julie Walters, meanwhile, are splashy scene-stealers as Donna's best friends and former backup singers, Tanya and Rosie. (Then again, the brassy Baranski is a musical theater veteran. This is her bread and butter.)

But not everyone fares so well. Pierce Brosnan and Stellan Skarsgard, as two of the potential dads, should never be allowed to sing in public again unless it's karaoke night and copious amounts of alcohol are involved. As Bachelor No. 3, Colin Firth has a touch more musical ability, but then his character is stuck with a contrived subplot that comes out of nowhere.

Ah yes, the plot -- there is one wedged in among all those ABBA songs. (Catherine Johnson, writer of the "Mamma Mia!" musical, also wrote the script. Fans of the show will be happy to see that it's a faithful translation.)

Sophie is about to marry her fiance, Sky (Dominic Cooper of "The History Boys"), but before she can begin a new life with him, she wants to know about her past. She digs through Donna's diary, reads about the three different men with whom mom was involved around the time she was conceived, and secretly invites them to her wedding.

Donna freaks out at the sight of them, which inspires her to -- what else? -- burst into singing "Mamma Mia." Pals Tanya and Rosie, formerly known as "The Dynamos," try to cheer her with "Chiquitita" and "Dancing Queen," and on it goes until the father is revealed. The songs have nothing to do with the action, mind you, except for a very literal use of "I Do, I Do, I Do, I Do, I Do," another one that gets trapped in your brain.

And yet the songs are the whole point, the reason crowds have been flocking to this show for years, and the reason the "Mamma Mia!" movie will probably turn out to be an enormous crowd-pleaser. No, most of the actors can't sing and none of them has anything approaching a Broadway-caliber voice, but they know that, and they know that we know that, and all that knowing gives the film a sort of roughhewn charm.

"Mamma Mia!" is a Universal Pictures release. It is rated PG-13 for some sex-related comments. Running time: 108 minutes. Two stars out of four.