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 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 PBS thing. And the excessive use of zooms was 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 greatest actress of our time writhing around in overalls on top of a barn or belting out numbers in a sparkly, spandex jumpsuit can indeed be a hoot.

Streep was a fan of the Broadway show, and her passion and enthusiasm explode on-screen. She can sing, a talent that's been on display in bits and pieces previously.

Amanda Seyfried 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.

But not everyone fares so well. Pierce Brosnan and Stellan Skarsgård, 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.

Sophie is about to marry her fiance, Sky (Dominic Cooper), but before she can begin a new life with him, she wants to know about her past. She digs through Donna's diary and secretly invites three men to her wedding.

Donna freaks out at the sight of them, which inspires her to burst into singing "Mamma Mia." Pals Tanya and Rosie 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, and yet they are the whole reason the movie will probably be an enormous crowd-pleaser. No, most of the actors can't sing, but they know that, and they know that we know that, and all that knowing gives the film a sort of roughhewn charm.