Metallica put out this perfect record in part because they were able to maintain the crushing force and velocity of their thrash origins by mixing up their lacerating riffs with unpredictable rhythms and upfront bombast. Brutal at any tempo, but with a Sabbath-lineage damnation of human cruelty in war (“Disposable Heroes”) and the mental health system (“Welcome Home (Sanitarium)”) and religion-for-profit (“Leper Messiah”), it’s metal’s take on Wagner with a conscience.

Not that there haven’t been better albums before or since, but this is it, the Pet Sounds/Straight Out Of Compton/ZOSO of its genre, the one album you would play visiting aliens to show them what metal was, is, and can be in all of its stupid ambitious sophomoric grandiose visceral glory. The San Francisco thrash quartet’s third album catapulted them to the top of the scene, and soon it’d be a mere stepping stone on their way to becoming the biggest hard rock band in the world. They’ve still never topped its elegant combination of power, emotion, and start-to-finish killer tunes.