Any metal music fan should immediately recognize this article’s title as misleading. What kind of metal music are we talking about? Even metal and heavy metal are separate categories despite the terms being used interchangeably.

To understand metal and how this music genre has changed over the years, we have to go back, even before metal’s early days. To a time when the music scene wasn’t sure which direction to take. To a time when technology first made metal music possible.

Finding the Metal Sound

No sooner did the first viable, affordable electric guitar hit the US market than guitar players started experimenting with its more gritty possibilities. In the 1950s, Memphis blues guitarists Willie Johnson and Pate Hare became power chord pioneers; a playing style that would come to underpin metal music.

In the 60s, UK musicians began experimenting with US blues music, often playing songs much faster than the original recordings. These cutting-edge musicians had to learn to play the guitar to suit this more dynamic sound but that proved to be only a small challenge. The Yardbirds were masters of this fast-tempo genre that came to be known as blues rock. The Kinks took a step further away from the Blues sound – and much closer to metal with their 1964 smash You Really Got Me.

During the mid to late 60s, the British music scene went in all directions at once. Acid rock, psychedelic rock and punk all flourished alongside more mainstream fare. Acts like Cream pioneered double bass drumming and unison riffing – the bass and guitar playing in tandem. Starting in the late 60s, proto-metal acts started with macabre, theatrical stage shows that incorporated what most considered satanic elements.

Early 70s metal acts like Alice Cooper and Black Sabbath made ample use of shock visuals as they continued to refine their sound. Of course, that meant Ozzy and his group had to revamp everything from their signature sound to their stage presentation. It was quite a pivot they made from the Polka Tuck Blues Band!

Depending on which side of the pond you’re on, there’s some disagreement over who the true first full metal act was. Led Zeppelin, Deep Purple and Black Sabbath are often lumped together as the ‘Unholy Trinity’ but the comparison doesn’t stand. The first two had a milder, bluesier vibe. Only Black Sabbath had all of the metal elements. But they didn’t play heavy metal until the late 70s.

The Heavy in Heavy Metal

In 60s Britain, ‘heavy’ was slang for ‘good’. It didn’t take too long for that meaning to hop across the pond and, soon, you could hear “That’s heavy, man!” wherever the counterculture gathered. Or simple “Heavy!” to describe anything from a good trip to bad news.

Using ‘heavy’ as slang just as metal music was gaining ground was purely coincidental. The ‘heavy’ in heavy metal references its ponderous sound, not a brand of music universally accepted as good.

However, there is some overlap. ‘Heavy’ was so common in everyday speech that songwriters started including it in their lyrics. It was also used to describe hard-hitting music, often interchangeably with ‘rock’ and ‘hard rock’. Black Sabbath made clear the distinction between hard rock and heavy metal clear with their 1970 debut album. Around that time, ‘heavy’ faded from the slang lexicon.

Metal Goes Mainstream

To be clear, throughout the 70s, Black Sabbath’s sound was still closer to rock than heavy metal but that’s only because the genre was still evolving. It wasn’t until the late 70s. when all the elements came together and blended with improved technology that it truly became heavy.

By that time, plenty of other bands had made a name for themselves on the underground music scene and were ready to go mainstream. Motörhead managed to fill the gap between metal and punk, another  genre that enjoyed commercial success in the mid- to late-70s. By contrast, Saxon and Iron Maiden kept their metal pure. Judas Priest and Ronnie James Dio, then with Black Sabbath, made the metal sound tougher.

Van Halen, though not a metal band, had a strong influence on the genre. They opened for Black Sabbath on their Never Say Die! tour in 1978. That’s when the wider music world got their first sampling of Eddie van Halen’s lightning-fast licks. His Eruption solo established him as one of the leading metal guitarists of the day.

Further Metal Evolutions

Was Van Halen a sign of the times? Or was it because the British music scene had moved on? In the early 80s, synth-pop became all the rage and, once again, UK musicians led the wave. Perhaps to compete with the flashy neon of the times, glam metal bands commanded US stages. Acts like Ratt, Mötley Crüe and Quiet Riot took the lead, producing commercially appealing music.

Europe, Poison, Cinderella and Warrant soon followed. They were fun and had easy-to-sing-with tunes; they also put out power ballads for their growing female fanbase. Metalheads were growing restless, though; they missed the more edgy fare. Guns’n’Roses delivered, recharging the metal scene and paving the way for Jane’s Addiction – one of the first groups identified as alternative metal.

Meanwhile, the underground metal scene was bustling. Thrash metal bands Metallica, Anthrax and Slayer hadn’t yet become household names but even in the early 80s, they pulled in sizable crowds. Slayer wasn’t quite as renowned as Megadeth, another major thrash band, but they directly influenced death metal.

Death metal is all about speed and aggression, with a penchant for screams, growls and dark lyrics. They shunned the glam look, leaning closer to grunge. Death, Possessed and Necrophagia were instrumental in establishing the genre.

Black metal also features shrieks and growls but their lyrics tend more towards pagan themes, though some dark elements remain. They also incorporate other genres into their music, including classical and avant-garde. This makes black metal harder to define as a specific sound.

By contrast, doom metal rejects all other metal iterations. No speed, no thrash, no glam and no stage theatrics. The tone is more melancholy and melodic. This metal genre got its start in the mid-80s but didn’t really take off until 1991, when Cathedral released Forest of Illusion.

That doom-death fusion opened the floodgates to other metal meldings. Today metal music counts everything from rap metal (metal with hip hop elements) to groove metal – Pantera’s signature sound. Nu metal is the most inclusive metal subgenre. It features aspects of rap, rock, funk and grunge.

More recently, Metalcore, a blend of extreme metal and hardcore punk has taken center stage. This genre has also been around since the mid-80s but only became commercially successful in the new millennium. It’s spawned many other ‘core’ iterations; deathcore, mathcore and melodic metalcore among them.

Where does metal go from here? Its only limits are technology and artists’ imaginations. And listeners’ preferences, of course. Retro-metal’s success has shown a longing for fundamental styles but the popularity of progressive metal and djent signal an audience craving ever more complex artistry and technical skills.