In the ’80s, let’s say you never grew a mullet, squeezed into acid-washed jeans or threw the horns at a Quiet Riot concert. Doesn’t mean that the pop hits of the period didn’t fuse with your hormones and secure an unassailable seat in your pleasure center. That sweet spot is exactly what the insanely fun mixtape musical Rock of Ages relentlessly tickles, with its familiar heavy-metal ballads married to an impish, self-mocking book. Think it’s just a cheap retro goof? Rock of Ages shatters irony with a killer drum solo, then melts the wreckage with a smoking guitar riff.