Mamma Mia! is a musical based on the stage musical of the same name, which is in turn based on the songs of ABBA, starring Meryl Streep, Amanda Seyfried, Skellan Skarsgard, Pierce Brosnan, Colin Firth, Julie Walters, Christine Baranski, and Dominic Cooper.
Sophie (Seyfried) is getting married very young to her boyfriend Sky (Cooper). She lives on a Greek island with her mother Donna (Streep) who runs a hotel/B&B kind of thing, but she's never known her father. Shortly before her wedding, she reads her mom's diary and learns that mom had...rather a busy summer 20 years ago. Sophie has three possible fathers: Sam (Brosnan), Bill (Skarsgard), or Harry (Firth). She invites them all to her wedding, figuring she's magically know her real dad on sight (what) and ask him to walk her down the aisle.
Of course, this does not go quite as planned, there's drama, Donna reconnects with her former lovers and confronts the fact that Sophie's being a little protective of her mother, but that her mother really does need someone around. And then Sophie and Sky decide they're far too young to marry, but Sam proposes to Donna, Bill hooks up with Donna's old friend Rosie (Walters), Harry, it turns out, is gay and finds a lovely young Greek man to snog, and all is well.
The movie maps pretty well from the show; they cut a couple of songs, but nothing that you miss. The mistake was casting Firth, Brosnan, and Skarsgard, none of whom can sing, and especially not next to Streep and Seyfried, who both really clearly can. Likewise, in a musical you get an intermission, and there are a lot of songs, even with the cut.
The performances are good, though, discounting the troubled vocals. They changed Harry from "happily in a relationship" to "met a dude on the island", but since that gives him someone to kiss during the last scenes, I'm kinda OK with it. The scenery is well-realized, too; the villa feels real and you learn your way around, which is always fun.
Overall, it's worth watching if you like ABBA and you're not going to get too bothered by the lead men's lack of singing chops.
My Grade: B
Rewatch value: Medium-low
Next up: The Man from UNCLE