Battery

Battery's harmonic identity is defined by the tension between its delicate acoustic E minor opening and the high-velocity thrash riff that follows. Rooted firmly in natural/Aeolian E minor, the song avoids jazz or blues coloring entirely, instead deploying chromatic power chord motion and modal flatted-seventh harmonies (♭VII D, ♭VI C) typical of heavy metal's classical-influenced darkness. The structural acoustic-to-electric contrast was a deliberate compositional choice that mirrored Fight Fire with Fire and became one of the most studied opening gambits in metal history.

Battery was written by James Hetfield and Lars Ulrich for Metallica's third studio album. Hetfield improvised the central thrash riff while relaxing in London, far from any formal rehearsal setting. The composition deliberately mirrors the structure of Fight Fire with Fire — the opener of their previous album Ride the Lightning — beginning with a delicate dual-acoustic guitar section before erupting into high-velocity thrash metal.

Battery opens Master of Puppets with a stunning acoustic-to-electric contrast that became a template for heavy metal intros. Built around James Hetfield's improvised riff and a theme rooted in San Francisco's underground thrash scene, it is both a community anthem and a technical showcase. Widely considered one of the greatest album openers in metal history, it defined what Metallica — and thrash metal as a genre — could achieve.