It goes back to the fricken blues. Rock music has always lived on the fringe of society and what makes it so appealing is it’s edginess and conflict with the morality of the dominant culture. A little bit of evil, sex, drugs and you have rock n roll. Doom is nothing more that the blues retooled. Death Metal is nothing more than lyrical and musical content taken to the extreme in order to alienate the masses. Of course playing very fast and loud, as well as slow and distorted helps the cause. The first group of bands that were originally classified as Heavy Metal were Black Sabbath, Led Zepplin and Deep Purple and the most metal sound releases were Master of Reality, Led Zep II and In Rock.
These bands influenced the next group consisting of Judas Priest, Queen and Kiss whose best albums are represented by Stained Class, Queen I and Hotter Then Hell.
After those great bands, enjoy the punk infused speed rhythm and blues of the great proto-thrash band Motorhead, Ace of Spade, then the transition to what I consider more modern heavy metal in the form of the NWOBHM giant, Iron Maiden, “The Number of the Beast”. But sitting at the top of the metal heap, are the undeniable gods of metal, the beyond reproachable, Slayer whose Rick Rubin produced “Reign in Blood”, is still the greatest thrash record, which automatically puts it at the top of best metal record, ever.