Is it possible to imagine the world before musicals? The feeling of being filled up with the goodness of life until not only do you burst into song, but the world around you starts dancing, too, is such an essential component of human existence that it’s no surprise it was invented by the Greeks, who also gave us democracy and Plato and now provide the sun-kissed locations for “Mamma Mia!” the movie version of the blockbuster Broadway musical based on the ABBA songbook.

On a glossy Greek isle, Sophie (Amanda Seyfried) is getting married and she wants her father to give her away. The only catch is that her mother, Donna (Meryl Streep), did quite a bit of sleeping around in the ’60s, and her father could be any of three possible candidates, none of whom she’s ever seen before. There’s Pierce Brosnan, Colin Firth, and Stellan Skarsgård to choose from, and so Sophie secretly invites them all to her wedding, blithely assuming that she’ll know her real father the second she lays eyes on him. Complications, needless to say, ensue.

Savvy viewers will realize what they’re in for the second they see that “Mamma Mia!” is produced by Tom Hanks and Rita Wilson, the parties responsible for “My Big Fat Greek Wedding,” which was loved and loathed in equal measure. In “Mamma Mia!” the actors run around screeching with delight as old friends arrive, cackling with laughter at jokes that aren’t very funny, and everything is shot in the bright, uninteresting colors of a Martha Stewart magazine layout. The camerawork is shaky, the lip-synching is shoddy, the choreography is nonexistent, and the whole thing is the best time I’ve had in a movie theater all summer.

While the technical aspects are important, there’s an intangible gusto that musicals need in order to really come alive, and “Mamma Mia!” has it in spades. Rarely have so many actors seemed to have such a great time in a film, and their joy is infectious. The ABBA songs are dropped into the movie (and, one assumes, the show) somewhat at random, but they’re all solidly built and well known and so the audience quickly gets over the fact that they only have a nodding acquaintance with what’s actually happening in the plot. For the most part they work, and even when a song is a clunker, it’s usually only seconds before another one is coming at you.

Ms. Streep anchors the proceedings and lends the silliness a lot more emotional heft than it warrants, which means that you’ll probably get all teary at least once. She’s having almost too much fun belting out the golden oldies, and watching how easily she maintains her dignity while doing so makes one wish she could pass on the secret to Robert De Niro and Dustin Hoffman, who aren’t approaching their late-career roles with a fraction of the grace she possesses. Ms. Seyfried has the expressive, malleable face of a musical-theater star, able to go from happy to heartbroken in one believable blink of the eye, and the male leads hold their own. But it’s two old pros, Julie Walters and Christine Baranski as Donna’s college pals, who steal the show. These two have been upstaging their co-stars since the stage was invented, and they show no sign of stopping now. Meryl Streep may bring the emotional nuance, but these two bring the musical-comedy timing, and that proves to be a more essential ingredient to keeping this big, awkward bird in the air.

“Mamma Mia!” has been getting generally good reviews, but it’s also been getting trashed by some critics who all have one thing in common: They’re men. If you don’t want to watch a documentary about the Iraq war this summer, or if you don’t want to watch special effects fight other special effects, then “Mamma Mia!” is just about the only game in town. It’s a movie that has more than its fair share of flaws, but when you watch an entire village drop its chores to join Meryl Streep singing “Dancing Queen” on a rustic pier, it’s hard to suppress that surge in your chest: When a musical does what a musical does best, it makes you feel like the whole world is so happy it’s got no choice but to burst out singing. Somewhat shoddy, slapdash, and silly? Sure. But it’s also stuffed with spectacular showmanship.