In a 1988 article, The New York Times critic Jon Pareles wrote, "In the taxonomy of popular music, heavy metal is a major subspecies of hard-rock—the breed with less syncopation, less blues, more showmanship and more brute force.

"[50] In an article written for Grove Music Online, Walser stated that the "1980s brought on ... the widespread adaptation of chord progressions and virtuosic practices from 18th-century European models, especially Bach and Antonio Vivaldi, by influential guitarists such as Ritchie Blackmore, Marty Friedman, Jason Becker, Uli Jon Roth, Eddie Van Halen, Randy Rhoads and Yngwie Malmsteen.

'"[53] According to David Hatch and Stephen Millward, Black Sabbath and the numerous heavy metal bands that they inspired have concentrated lyrically "on dark and depressing subject matter to an extent hitherto unprecedented in any form of pop music."

They take as an example Black Sabbath's second album, Paranoid (1970), which "included songs dealing with personal trauma—'Paranoid' and 'Fairies Wear Boots' (which described the unsavoury side effects of drug-taking)—as well as those confronting wider issues, such as the self-explanatory 'War Pigs' and 'Hand of Doom.

[58] Music critic Robert Christgau called metal "an expressive mode [that] it sometimes seems will be with us for as long as ordinary white boys fear girls, pity themselves, and are permitted to rage against a world they'll never beat".

In addition to its sound and lyrics, a heavy metal band's image is expressed in album cover art, logos, stage sets, clothing, design of instruments and music videos.

[69] Originally adopted from the hippie subculture, by the 1980s and 1990s, heavy metal hair "symbolised the hate, angst and disenchantment of a generation that seemingly never felt at home", according to journalist Nader Rahman.

[73] Pioneered by the heavy metal act X Japan in the late 1980s, bands in the Japanese movement known as visual kei, which includes many non-metal groups, emphasize elaborate costumes, hair and makeup.

"[89] Inspired by Burroughs' novels,[90] the term was used in the title of the 1967 album Featuring the Human Host and the Heavy Metal Kids by Hapshash and the Coloured Coat, which has been claimed to be its first use in the context of music.

"[95][nb 1] Another appears in the 11 May 1968 issue of Rolling Stone, in which Barry Gifford wrote about the album A Long Time Comin' by U.S. band Electric Flag: "Nobody who's been listening to Mike Bloomfield—either talking or playing—in the last few years could have expected this.

[98] In January 1970, Lucian K. Truscott IV, reviewing Led Zeppelin II for the Village Voice, described the sound as "heavy" and made comparisons with Blue Cheer and Vanilla Fudge.

[117][118] Where the blues rock drumming style started out largely as simple shuffle beats on small kits, drummers began using a more muscular, complex and amplified approach to match and be heard against the increasingly loud guitar.

In July, the Jeff Beck Group, whose leader had preceded Page as The Yardbirds' guitarist, released its debut record, Truth, which featured some of the "most molten, barbed, downright funny noises of all time", breaking ground for generations of metal ax-slingers.

[145] In this counterculture period, MC5, who began as part of the Detroit garage rock scene, developed a raw, distorted style that has been seen as a major influence on the future sound of both heavy metal and later punk music.

[172] In 1973, Deep Purple released the song "Smoke on the Water", whose iconic riff is usually considered as the most recognizable one in "heavy rock" history, as a single of the classic live album Made in Japan.

"[180] The issue is not only one of shifting definitions, but also a persistent distinction between musical style and audience identification; Ian Christe describes how the band "became the stepping-stone that led huge numbers of hard rock fans into heavy metal perdition".

Objections were raised to metal's adoption of visual spectacle and other trappings of commercial artifice,[183] but the main offense was its perceived musical and lyrical vacuity: reviewing a Black Sabbath album in the early 1970s, Robert Christgau described it as "dull and decadent ... dim-witted, amoral exploitation.

[214] Though less commercially successful than the rest of the Big Four, Slayer released one of the genre's definitive records: Reign in Blood (1986) was credited for incorporating heavier guitar timbres and including explicit depictions of death, suffering, violence and occult into thrash metal's lyricism.

[230] Complementing the deep, aggressive vocal style are down-tuned, heavily distorted guitars[228][229] and extremely fast percussion, often with rapid double bass drumming and "wall of sound"–style blast beats.

[228] The first wave of black metal emerged in Europe in the early and mid-1980s, led by the United Kingdom's Venom, Denmark's Mercyful Fate, Switzerland's Hellhammer and Celtic Frost, and Sweden's Bathory.

[236] Around 1996, when many in the scene felt the genre was stagnating,[240] several key bands, including Burzum and Finland's Beherit, moved toward an ambient style, while symphonic black metal was explored by Sweden's Tiamat and Switzerland's Samael.

[247] Many power metal bands such as the U.S.'s Kamelot, Finland's Nightwish, Stratovarius and Sonata Arctica, Italy's Rhapsody of Fire and Russia's Catharsis feature a keyboard-based "symphonic" sound, sometimes employing orchestras and opera singers.

[272] Metalcore, a hybrid of extreme metal and hardcore punk,[273] emerged as a commercial force in the mid-2000s, having mostly been an underground phenomenon throughout the 1980s and 1990s;[274] pioneering bands include Earth Crisis,[275][276] Converge,[275] Hatebreed[276][277] and Shai Hulud.

[285][286] Established continental metal bands that placed multiple albums in the top 20 of the German charts between 2003 and 2008 include Finland's Children of Bodom,[287] Norway's Dimmu Borgir,[288] Germany's Blind Guardian[289] and Sweden's HammerFall.

[314][315] Laina Dawes explored the multidimensional components of racism in her book What Are You Doing Here?, including the perspectives of black women musicians and fans, in the heavy metal scene in North America and the United Kingdom.

She also grounded her doctorial thesis "'Freedom Ain't Free': Race and Representation(s) in Extreme Heavy Metal" on her own experiences, laying out some the nuances of a community that can be both a site of exclusionism and at the same time also a place for greater freedom of expression compared to mainstream genres.

In 1994, Liv Kristine joined Norwegian gothic metal band Theatre of Tragedy, providing "angelic"[328] female clean vocals to contrast with male death growls.

[331] The most notable of these 1990s/2000s female-fronted groups was the American band Evanescence, headed by vocalist Amy Lee and featuring a musical style usually described as gothic alternative metal and hard rock with classical elements.

[332] Their first album Fallen, released in 2003, broke into the popular music scene and was a worldwide phenomenon;[333] it earned the band two Grammy Awards and briefly catapulted Lee to a level of fame similar to that of contemporary popstars such as Christina Aguilera, Avril Lavigne, and Beyoncé.

Citing her own research, including interviews of British female fans, she found that metal offers them an opportunity to feel liberated and genderless, albeit if assimilated into a culture that is largely neglectful of women.