As demonstrated by song titles like "I Love the Spirit World and I Love Your Father,” San Francisco instrumental metal trio The Fucking Champs have a sense of humor. But IV shows they’re no joke. "Esprit de corpse" has riffs catchy enough to hum and a triumphant uplift, and "Thor Is Like Immortal" oscillates between a playful, chicken-scratch metal riff and emotional downturns. "What's A Little Reign?" marries near-mathematical chord changes with a groove solid enough to knock out anything in its way.