Heavy metal, as a genre, has become woefully misunderstood and underappreciated in recent years, as its dozens of subgenres have fragmented and evolved away from the intense-yet-accessible nature of its roots. What began as late-60s experiments with guitar distortion among blues-rock bands has now become one of the most diverse genres around, and yet many modern metal acts have lost sight of those roots, leaving classic metal on the brink of being just a reference in 80s movies.

The original waves of heavy metal as shown in documentaries like Dio: Dreamers Never Die were absolutely a product of their time, and while modern music production has now heavily shifted in favor of singles and EPs over full albums, classic metal has always been best when listened to cover-to-cover. So find a proper stereo, plug in some over-the-ear headphones, and let the gods of rock transport you back to the golden age of heavy metal.

10 In The Court Of The Crimson King

King Crimson, 1969

While technically a progressive rock band, King Crimson were heavily influential to the DNA of heavy metal, and nowhere else is this more apparent than their semi-eponymous debut In the Court of the Crimson King. All the prototypical elements of metal are here on this album — intense rhythms, phenomenal guitar riffs, esoteric and mythological imagery — and they coalesce into something that could be described as a relentless assault on the senses.

Out of the five songs on the album, two stand out as true primogenitors of metal. The opening track, "21st Century Schizoid Man," plays with meter throughout its 7:24 runtime until reaching a chaotic climax inspired by the big-band sound of Duke Ellington's orchestra, and yet the half-century-old riffs are undeniably metal at their core. The same goes for "The Court of the Crimson King" itself, a nine-and-a-half-minute epic that defies description and clearly had a profound influence on Stephen King's entire body of work.

9 Paranoid

Black Sabbath, 1970

While Black Sabbath's first album is generally considered the first true heavy metal album ever released, it's the band's sophomore outing — released only seven months later — that is a start-to-finish masterpiece. Some of Sabbath's most iconic songs, like "Iron Man" and "War Pigs," come from this album, but there isn't a sleeper to be found (partially because "Behind the Wall of Sleep" was on Black Sabbath instead).

Paranoid was also historically important because of its place in the controversy fueled by the Moral Majority movement in the 1980s, as they attempted to stamp out any music they deemed as Satanic. Lyrics to "Hand of Doom" and "War Pigs" were held up as an example of the forces corrupting the morality of young people, even though the songs are clearly written as cautionary tales about the dangers of drug addiction and the Vietnam War. So, because of both its historical importance and its truly legendary licks, Paranoid remains one of the most essential albums of early metal.

8 IV

Led Zeppelin, 1971

Led Zeppelin's fourth studio album is technically untitled, as guitarist Jimmy Page decided, in response to Led Zeppelin III's mediocre reception, to depart from the numbering convention the band had previously used. Instead, each member of the band chose or created a symbol to represent themselves, and those four symbols technically made up the record's title. As a result, while still commonly called Led Zeppelin IV by the band and fans to this day, the album is also known as ZoSo (which is what Page's symbol appears to read as), Four Symbols, Untitled, and even Runes.

Whatever the title, Led Zeppelin's fourth release remains one of their most cohesive and heaviest records. The opening moments of "Black Dog" begin with a tape of guitars being spun up to speed before suddenly cutting out, only for Robert Plant's shrieking "hey, hey mama" to slap you across the ears and get you to pay attention, and the album's pace never slows from there.

"Stairway to Heaven" has become one of the most iconic rock songs of all time. "The Battle of Evermore" and "Misty Mountain Hop" both continue the trend begun with Led Zeppelin II's "Ramble On" with lyrics referencing the works of J.R.R. Tolkien. And the album's closer, "When the Levee Breaks," is a reworked version of a blues track from 1929 by Memphis Minnie and Kansas Joe McCoy, reincarnating the original into an intense, pounding, seven-minute epic.

7 Machine Head

Deep Purple, 1972

While Deep Purple, like so many early metal bands, began as a progressive rock outfit, by the time they began recording their sixth album Machine Head, they had refined their sound through four years of intense live gigs, and returned to the studio with the goal of recapturing their intense live sound on tape. Using the Rolling Stones Mobile Studio, a truck loaded with recording equipment and owned by the Stones (although other bands, particularly Led Zeppelin, had begun using it as well), they headed to the Montreaux Casino in Switzerland, which often rented itself out as a recording studio.

Fate intervened in a bizarre way when the Montreaux Casino caught fire the day before Deep Purple began recording. Frank Zappa and the Mothers of Invention were performing there when one of their fans fired off a flare, sending the building up in flames. Deep Purple had been drinking at a bar nearby and saw the fire happen, which inspired them to write the song "Smoke on the Water" and put it on Machine Head, and the rest is history. The rest of the album is also phenomenal, with "Highway Star" and "Space Truckin'" standing out as particularly heavy.

6 Demons And Wizards

Uriah Heep, 1972

Demons and Wizards was the British rock group's first release with bassist Gary Thain, and the chemistry among Uriah Heep's is audible throughout the album. With a sound that critics described as "sullen" and solitary," but also "the finest high-energy workout of the year," this album further helped crystallize the link between heavy metal and strangely fantastical lyrics.

The album's lead single, "The Wizard," was Uriah Heep's first music video, and is a very Zeppelin-esque acoustic ballad about meeting a royal wizard. Second single "Easy Livin'" is one of the most widely covered Uriah Heep songs since its release, and is a solid representation of the album as a whole. Keyboardist Ken Hensley described in Demons and Wizards' liner notes as "just a collection of our songs that we had a good time recording," and that joy is evident throughout the album.

5 Spectres

Blue Öyster Cult, 1977

The psychedelic rock quintet's fifth album, Spectres was certified gold within two months of its release at the end of 1977. Riding the high of the previous year's Agents of Fortune, which catapulted the band into the public eye with the single "Don't Fear the Reaper," BÖC put together a second smash album that started off with a literal bang in opening track "Godzilla," a single that has long since been platinum-certified.

It took 42 years for "Godzilla" to be used in an actual Godzilla film, when System of a Down frontman Serj Tankian (aided by Dethklok's real-life frontman Brendon Small and drummer Gene Hoglan) covered the song for the soundtrack of 2019's Godzilla: King of the Monsters.

The rest of Spectres is full of songs that embody the hard-partying vibes of heavy metal, from the biker-bar anthem "Golden Age of Leather" (which opens with a rousing verse from the Newark Boys' Chorus) and the self-aware "R. U. Ready 2 Rock" to the album's closer, the moody vampire jam "Nosferatu." While Blue Öyster Cult is sometimes considered a gimmick band, in no small part thanks to their lampooning on Saturday Night Live, Spectres shows that behind that sense of humor lies a beating heart of pure metal.

4 No Sleep 'Til Hammersmith

Mötorhead, 1981

Recorded during 1981's Short Sharp Pain in the Neck tour, Mötorhead's first live album is a collection of eleven unhinged, raw, sometimes even primal renditions of tracks from their first four studio albums. The tour was so named after drummer Phil Taylor was dropped on his head as the band were roughhousing after a gig, although it also describes the aftereffect of too much headbanging, which is a common ailment after listening to Mötorhead.

Vocalist and bassist Lemmy Kilmister is considered one of the true gods of metal, and Mötorhead played live right up until his death from cancer in December of 2015. But in 1981, before decades of heavy metal debauchery took their toll, Kilmister was on the top of his game, playing some of the most brain-melting bass riffs anyone had ever heard. No Sleep 'Til Hammersmith serves as an early "best of" compilation for Mötorhead, and is the kind of nonstop assault on the senses that reminds listeners that heavy metal is something that can bludgeon just as easily as shred.

3 Borrowed Time

Diamond Head, 1982

While the hard-rocking quartet of Diamond Head had already released a full album on an independent label, Borrowed Time was their first of two releases on major label MCA. Diamond Head were never one of the more globally popular bands from the late 70s wave of British heavy metal, but they were incredibly influential on the bands that followed them, particularly American thrash metal bands like Metallica and Megadeth.

Borrowed Time was Diamond Head's first and only album to chart, reaching number 24 in the UK, and was the source of several of the band's most enduring live hits ("In the Heat of the Night," "Don't You Ever Leave Me"), as well as more polished versions of "Lightning to the Nations" and "Am I Evil?" which had both appeared on their debut Lightning to the Nations. "Am I Evil?" is easily Diamond Head's most famous song; it was never released as a single, but in 1984 Metallica covered it for the B-side of their single "Creeping Death."

2 Number Of The Beast

Iron Maiden, 1982

The Number of the Beast is the album that catapulted Iron Maiden from just one of many bands in the New Wave of British Heavy Metal to international stardom that still continues to this day. It was vocalist Bruce Dickinson's first release with the band, and his new vocal style helped make The Number of the Beast the first Iron Maiden album to top the UK Albums Chart and hit the US Billboard Top 40. The first single, "Run to the Hills," was also Maiden's first top-ten single in the UK.

From its opening song, "Invaders," to the bombastic outro of the closer "Hallowed Be Thy Name," The Number of the Beast is a truly flawless album. Its open use of Satanic symbolism painted a target on Iron Maiden's back and led to public burnings of the album, but that only resulted in more publicity, with sales hitting gold in only a year, with platinum certification following soon in 1986. Since then, The Number of the Beast has repeatedly proven itself to be one of the greatest metal albums of all time, having sold at least 20 million copies and counting.

1 Holy Diver

Dio, 1983

Ronnie James Dio was already one of the great vocalists of heavy metal by the time Holy Diver was released. It was the first album of Dio (the band), but Dio (the man) had been involved in heavy metal since 1975, when Deep Purple's founding guitarist Ritchie Blackmore started a new band, Rainbow, inviting Dio and his then-bandmates from Elf to the project. After leaving Rainbow in 1979, Dio replaced Ozzy Osbourne as the lead singer for Black Sabbath, recording three albums with the legendary band until he departed in 1982 over creative disagreements and started his own project.

Holy Diver shows Dio's mastery of the genre, as well as its cultural roots, with riffs that crunch like broken bones and lyrics that aim to skewer hypocrisy in the establishment, particularly organized religion. Although his work with Elf in the 70s used fantastical elements, Holy Diver is Dio after having ed through the crucibles of both Deep Purple and Black Sabbath, and as a result the entire album thrums with life and power, particularly in the title track and the album's second single, "Rainbow in the Dark."