Equal parts pathos and schadenfreude, director Sacha Gervasi’s 2008 sleeper hit trails thrash-metal’s aging coulda-beens as they bicker, bungle tour arrangements, sleep rough, remortgage their homes, disappoint their loved ones and play to tumbleweed at Transylvanian metal festivals. Warning: this film may make you reconsider your proposed career in rock ’n’ roll.