The story of metal is not linear. We didn’t arrive at the mayhem lurking in our Spotify playlists through a measured progression of technique, style, and genre. Rather, the evolution came in leaps and bounds, with dead ends and bursts of growth and pockets of innovation. To continue the evolutionary metaphor: the Cambrian Explosion of metal shot off in the mid 1980’s, as subgenres and geniuses and success combined into a specimen closely resembling much of modern metal. But the growth, although frantic, wasn’t instantaneous; rather, it seemed to expand exponentially from a single source, a catalyst in a chain reaction. That incipient band, the patient zero of metal as we know it today, is Iron Maiden. More precisely, the stratospheric success of The Number of the Beast, with it’s intricate compositions, transgressive lyrics, and trailblazing progressivity, diverged metal from hard rock completely and legitimized metal as a commercial viability, heralding the eruption of metal in the years to follow.