Yes, many critics will point to "Paranoid" as being their significant landmark album, but "Master of Reality" started to show the band leaving a hard rock sound in favor of a darker, heavier sound. Say what you will about who came before them, Black Sabbath is arguably THE first heavy metal band and the yard stick for which all other metal bands are measured.

Is it metal? Is it punk? It's one of the albums that helped facilitate thrash, crossover, and metalcore with their metal sound and DIY work ethic.

Abrasive and well before it's time, this album provided the template from which extreme metal was born from.

The pop/glam metal era is one of the two more forgettable eras of the genre. Not too many acts came out that were both glam-looking and truly heavy, but this release by Motley Crue was definitely the most remarkable album of that genre and era.

Many will point to Metallica's Black Album as their magnum opus, but this album (the last with legendary bassist Cliff Burton) was able to attract fans with a lot less promotion behind it. This album is a metal masterpiece.

Grindcore comes to form with Napalm Death's debut album, recorded with virtually two different bands nonetheless.

Yeah, Priest had been around since nearly the beginning, but one listen to the intro of this album (the first with Scott Travis) makes this an all-and-all solid metal album.

Death metal comes alive in Florida, and no less of an influence on the album is... Mozart?!

While this band came out during the grunge era, they were at the forefront of the stoner metal movement.

While their earlier releases are considered by many to be more relevant to the genre, the band's first album with John Bush not only demonstrated the serious side of Anthrax, but also provided the song "Only", which James Hetfield of Metallica described as the perfect song.

Chuck Schuldiner's contributions to extreme metal cannot go ignored. One good listen and you'll notice where some of today's bands got their influences from.

This album broke significant ground in establishing the Gothenberg sound that is largely associated with Swedish Melodic Death Metal.

While the band themselves don't consider themselves to be metal, it's hard to ignore the influence this album had on the future acts of the genre.

Like glam metal, nu-metal was the other era that metal would like to forget it was part of. Yet in between all of the backward hats, 5 string basses, and rapped lyrics, this album came out and delivered a stunning approach to the genre.

This is one of the landmark black metal albums ever produced, which is remarkable considering that Immortal was at their most frail state at the time of creating the album. This album is purely brilliant.

What do you get when you mix Mike Patton, Buzz Osborne, Trevor Dunn, and the great Dave Lombardo? One wacky album that's all over the place!

With high-flying solos and furious drums traded in for atmospheric sounds, Isis's "Oceanic" gave creation to the post-metal genre.

Flame me all you want for putting this up here; name me one other power metal band who can capture your attention the way Dragonforce does!

Make no mistake, Machine Head's "Burn My Eyes" is a significant album to the genre of metal. But the lineup that recorded this album are not only a close-knit unit, but also managed to release one of the innovating albums of the neo-thrash movement.

Though largely considered hardcore, the pedigree and style of the band is as metal as any other group I could put here.