After emerging in the early ’70s, metal spent its first decade or so gaining speed—literally and figuratively—before any outside influences began shaping its sound. But once punk and hardcore entered the mix in the early ’80s, they opened the floodgates for more extreme forms of experimentation within the genre. In the Pacific Northwest, the Melvins laid the gooey groundwork for both sludge and grunge. Over in the UK, Godflesh fused metal with industrial music. In the Bay Area, Faith No More brought art rock, funk, thrash, and rap together in a beguiling union. The same spirit of innovation, fusion, and experimentation is apparent in Oxbow’s electrifying mix of noise rock, blues, and musique concrete; in Genghis Tron’s dizzying mashup of IDM, extreme metal, and electronic music; and in Zeal & Ardor’s unprecedented combination of black metal and African American spirituals.