In the late Sixties there were few quibbles from anyone about the merits of Cream or the Jimi Hendrix Experience. But when those bands retired and the old R&B movement collapsed the club goers were left gasping for musical sustenance. There was nothing for them in the jazz-rock experiments of Miles Davis and John McLaughlin, while bands like Traffic were too introverted for their taste.

To make matters worse, as soon as new, exciting bands like Led Zeppelin and Emerson, Lake and Palmer emerged, they went swiftly off to the States. Nevertheless, Zeppelin in particular would be an abiding influence on the way workaday bands would play for the next decade; their example helped give rise to a whole new breed of musicians as heavy rock became hard rock and, finally, heavy metal.

The key to the development of heavy rock was the rhythm section, the engine room of the movement. Well into the late Sixties, creative drummers tended to be a wild, undisciplined lot. Cream's Ginger Baker could lay down a steady beat but was never anxious to be soloing, while The Who's Keith Moon epitomised the 'one-man riot' approach to drumming. Even the most advanced drummers, such as Aynsley Dunbar, Mitch Mitchell and Ian Paice, were prone to self-indulgence. As a result, the raw energy of many new bands was dissipated in a clash of styles and egos as guitarists and drummers simply tried to play faster and louder than each other. John Bonham and Jimmy Page showed a better way.
With the example of Zeppelin's first album before them, rock musicians began to learn how to play together in cohesive fashion. Bass guitars and bass drums began to lock together, the lead guitarist stopped filling in every space and the singer attempted to make himself heard clearly, while keyboard and sax players took a back seat or disappeared altogether.

One of the first bands to describe themselves as 'heavy' were Spooky Tooth. The track from their first album, Waitin' for the World, was distinguished by Mike Kellie's drum introduction, which relied on the simplest bass and snare-drum beats. By 1972 British rock bands had begun to sound very tight indeed, as demonstrated by the Jeff Beck group on recordings such as Rough and Ready featuring Cozy Powell on drums.

The American band Grand Funk Railroad was one of the early proto-heavy metal bands (along with for example The Who) who set new benchmarks for volume levels during shows. The volume of the music was seen as the important factor rather than its musical qualities; though this influence is often denigrated as pointless extravagance, it has proven enormously influential and still dominates many people's perceptions of the genre. Motorhead and Manowar are more recent examples of bands that pride themselves of keeping the volume very high.

Those heavy-rock bands that preferred to work in Britain soon gathered loyal followings. The audience's sense of identification with the music was fuelled by the critical scorn with which much heavy rock was viewed upon by the "media intellectuals". One of the most consistently reviled groups was Black Sabbath. They became the band that the critics loved to hate, while their fans cheered and followed them all the way from Birmingham pubs to the Royal Albert Hall. The growth of heavy rock had nothing to do with record sales, chart hyping or media promotion, yet the more this movement grew the more it was ignored. Although hard rock sprang out of the clubs and pubs, it found its best place of expression at open-air festivals. Here the faithful could gather, drink, cheer and chant in a pubic display of enthusiasm that was always, surprising the usual hoards of security, peaceful. The violence was reserved for the stage, where guitar heroes played even louder and faster and singers screamed even higher.

If Robert Plant had strained to the limit of vocal endurance with Zeppelin, then his successors, like Ian Gillan, determined to go even further. Gillan came to fame with Deep Purple. With his huge vocal range, and let's not forget the sweatbands, he became the archetypal heavy rock figurehead. The New Wave of British Heavy Metal (NWOBHM) emerged in the late 1970s and reacted against the artifice of contemporary pop, placing an emphasis on musicianship and amplification, the former trait setting it apart from punk. Yet, unlike progressive rock, which placed a far greater emphasis on musical ability, and unlike post-punk, which emphasized 'strangeness' and innovation, the NWOBHM thrived on volume, speed, and directness, with an idealised working class image. Reviled or ignored by many mainstream critics in both the UK and the US, the NWOBHM nonetheless came to dominate the hard-rock scene of the early-mid 1980s.

The movement was most associated with Judas Priest, Iron Maiden, Def Leppard, Saxon, and Diamond Head, along with hard rock acts such as Motörhead and AC/DC which were not strictly part of the NWOBHM (and, in the latter case, not actually British). Judas Priest, Iron Maiden and Def Leppard went on to considerable, lasting mainstream success, with Def Leppard in particular being embraced by the American market. NWOBHM was musically characterised by power chords, fast guitar solos and screeching vocals, with lyrical themes often, drawing inspiration from mythology, fantasy fiction, and the occult. The movement's music was, however, often surprisingly melodic, and surprisingly parallel to punk and post-punk (the main riff in Def Leppard's 'Photograph' was taken from The Pretenders' 'Brass in Pocket,' which was itself one of several Pretenders songs built on the riff from Public Image Limited's 'Public Image.')

The NWOBHM existed mostly outside the world of mainstream pop and rock culture; magazines such as The NME, Sounds, The Face and Melody Maker did not generally feature NWOBHM acts at all, whilst the genre did not lend itself to success in the pop singles market; NWOBHM acts typically emphasised albums. In response to this lack of recognition a popular subculture of NWOBHM magazines and fanzines emerged, most notably Kerrang!. NWOBHM suffered the same fate as many other musical movements; the majority of its leading lights were unable to follow up their initial successes and the superstars moved further away from the genre towards mainstream hard rock. The few NWOBHM acts which remain popular today, with the exception of most notably Iron Maiden, are increasingly nostalgia acts.

By the middle and end of the 1980s, America had become the epicenter of heavy metal, most notably with Van Halen, and later with Guns N' Roses and Metallica. Heavy metal would return full circle through the pop vanity of the L.A. scene, led by Mötley Crüe. In the beginning, this form was led by legends like Judas Priest, Dio, Dokken and Twisted Sister. During the 1980s, a pop-based form of hard rock, with a party-hearty spirit and a glam-influenced visual aesthetic (sometimes referred to as "hair metal" due to the long and painstakingly-styled hair of band members) dominated the music charts in some parts of the world, and superstars like Def Leppard, Poison, Bon Jovi, Mötley Crüe, and Ratt helped lead the way. While their music has endured as representative of a particular view, time and place, this form is not always seen by metal purists as a particularly pure or well-executed form of metal. The 1987 debut of Guns N' Roses, a hard rock band with its Aerosmith influences worn prominently on its sleeve, and whose image reflected the grittier underbelly of the Sunset Strip, was at least in part a reaction against the overly-polished image of hair metal, but that band's wild success was in many ways the last gasp of the L.A. hard-rock and metal scene.

The explosion of guitar virtuosity (pioneered by Jimi Hendrix a musical generation earlier) was brought to the fore by Eddie Van Halen, and many consider his 1978 solo "Eruption" (Van Halen, 1978) a milestone. Ritchie Blackmore (formerly of Deep Purple), Randy Rhoads (with pioneers Ozzy Osbourne and Quiet Riot) and Yngwie Malmsteen went on to solidify this explosion of virtuoso guitar work, and in some cases, classical guitars and nylon-stringed guitars were played at heavy metal concerts. Classical icons such as Liona Boyd also became associated with the heavy metal stars as peers in a newly diverse guitar fraternity where conservative and aggressive guitarists could come together to "trade licks". This explosion would cool down in the music of Ronnie James Dio (who himself had a tenure at lead vocals with the legendary Black Sabbath) and continue to settle towards Judas Priest and Iron Maiden, who may be the final and complete consummation of "pure" heavy metal in the lineage of the "grandfathers" - Hendrix, Black Sabbath, Led Zeppelin and Deep Purple. After Iron Maiden, metal would push the limits of aggressive loudness in thrash metal, speed metal, black metal and death metal.

During the 1980s, a pop-based form of hard-rocking heavy metal (sometimes referred to as "hair metal" due to the long, curled hair of band members) dominated the music charts in some parts of the world, and superstars like Guns N' Roses, Def Leppard, Poison, Mötley Crüe, and Ratt helped lead the way. While their music has endured as representative of a particular view, time and place, this form is not always seen by metal purists as a particularly pure or well-executed form of metal. By the mid-1980s, as the term "heavy metal" became the subject of much contestation, heavy metal had branched out in so many different directions that new sub-classifications were created by fans, record companies, and fanzines, although sometimes the differences between various sub-genres were unclear, even to the artists purportedly belonging to a given style. Notable early 80s sub-genres where the overarching term "heavy metal" is occasionally still in use include the faster thrash metal, pioneered by the 'Big Four Of Thrash' (including Anthrax, Megadeth, Metallica and Slayer, with San Francisco quintet Testament sometimes being included in this group), and a hard-edged form of pop-metal from bands like Guns N' Roses and Def Leppard that brought pop-friendly music to mainstream audiences (to a mix of critical acclaim, mainstream popularity and purist disapproval).

Later styles of heavy rock music in the 1990s, such as the Seattle Sound (popularly, albeit incorrectly, referred to as Grunge) show influences of heavy metal but are typically not labelled sub-genres of heavy metal, as opposed to thrash metal and hair metal. The general absence of virtuosic guitar solos is perhaps one reason these bands have not been considered heavy metal bands. This sound appeared as a popularised endpoint of the punk rock-influenced alternative rock music of the 1990s which fought any mainstream influence (seen as "selling out") particularly reacted against overly-aggressive and increasingly formulaic hair metal bands from Ratt to Extreme. It evolved out of Seattle in the work of Mudhoney, Alice In Chains, Nirvana, Pearl Jam and Soundgarden.