In terms of pop-music history, the Runaways were both a groundbreaking band—all-female, protopunk, launching Joan Jett's solo career, and presaging riot-grrrl—and a prefab novelty act whose greatest hit was "Cherry Bomb." They were loud, brash rock 'n' roll, not particularly concerned with subtlety, nuance, or smarts—and in that regard, The Runaways is exactly the biopic they deserve.
It's no news that band biopics are perilously prone to cliché, but The Runaways cranks it to 11. Jett goes for guitar lessons: She wants to plug into an amp and learn to play like Chuck Berry—but her teacher tells her, "Girls don't play electric guitars," attempts to instruct her on an acoustic, and then stammers and sputters as she plugs into an amp anyway and proceeds to ROCK OUT! A band of mean old hippie rocker beardos kills the Runaways' first sound check on tour, kicks them off the stage, and says some stuff about playing with the big boys. At one point, when she's feeling dejected, Jett walks around alone to the tune of James Brown's "It's a Man's Man's Man's World." DO YOU GET IT?
To be fair, it's not like sexism wasn't/isn't a pervasive problem in the music world or that the Runaways weren't kicking down doors (even as they were being exploited as a novelty), and no doubt these incidents were inspired by real-life problems (the film is based on singer Cherie Currie's autobiography). But that doesn't make it any less trite on-screen.
Far more interesting, both in terms of gender politics and casual film viewing, is the relationship between the adolescent all-girl band and their male manager, Kim Fowley, a manipulative, amoral industry creep with an unconventional and highly quotable management style. Some of his better bons mots: "Men don't wanna see women anywhere but in their kitchens or on their knees, let alone onstage playing guitars!" "You bitches have got to start thinking like men—men wanna fuck!" "I'm gonna teach you prima donnas how to think with your cocks!" He tells them the Runaways are "the sound of hormones raging" and that "this isn't women's lib, this is women's libido!" He calls them "bitches," "pussies," etc. He tells them, "You're not employees; you're my property." He infamously trains them for heckling by having guys throw mayonnaise at them during rehearsal. Meanwhile, he tells the press that the band is about "self-empowerment—Cleopatra, Aphrodite."
The film introduces its frontwomen with Currie getting her period and Jett being scolded for trying to buy leather pants from the men's section of a vintage shop—Currie is the barely adolescent sexual being/object; Jett is the determined smasher of gender roles. Dakota Fanning ably disappears into her role as Currie (scouted for the band by Fowley, who thought they needed a "sex kitten": "Jail fucking bait, jack fucking pot!"); Kristen Stewart's Jett is believably tough and pouty in a way that her Twilight heroine has never been (and the scenes of her making out with Currie or teaching her bandmate how to masturbate to the thought of Farrah Fawcett should be instructive for fans of chaste, crypto-Mormon vampire melodramas). But Michael Shannon's Fowley steals the show—looking like Dwight from The Office in 1970s Los Angeles glam (the period sets and costumes are great)—and despite all the sex and drugs and musical montages, the film suffers when the girls go out on the road without him. For a film about a groundbreaking girl band, it's still sadly a man's world. 
