Glam metal (also known as hair metal or pop metal) is a subgenre of heavy metal that features pop-influenced hooks and guitar riffs, upbeat rock anthems, and slow power ballads. It borrows heavily from the fashion and image of 1970s glam rock.

Early glam metal evolved directly from the glam rock movement of the 1970s, as visual elements taken from acts such as David Bowie, T. Rex, and New York Dolls (and to a lesser extent, the punk and new wave movements taking place concurrently in New York City) were fused with the decidedly more heavy metal leaning and theatrical acts such as Alice Cooper and Kiss. The first examples of this fusion began appearing in the late 1970s and early 1980s in the United States, particularly on the Los Angeles Sunset Strip music scene. Early glam metal bands include Mötley Crüe, Hanoi Rocks, Ratt, Quiet Riot, Twisted Sister, Bon Jovi, and Dokken. Glam metal achieved significant commercial success from approximately 1982 to 1991, bringing to prominence bands such as Poison, Skid Row, Cinderella, and Warrant. From a strictly visual perspective, glam metal is defined by flashy and tight-fitting clothing, makeup, and an overall androgynous aesthetic in which the traditional "denim & leather" aspect of heavy metal culture is replaced by spandex, lace, and usually heavy use of bright colours.

Glam metal suffered a decline in popularity in the early-mid 1990s, as the grunge and alternative phenomena revolutionized hard rock, and fans' tastes moved toward a more natural and stripped-down aesthetic and a rejection of the glam metal visual style. During this period, many of the most successful acts of the genre's 1980s pinnacle suddenly found themselves facing disbandment as their audiences moved in another direction. Glam metal has experienced a resurgence since the late 1990s, with successful reunion tours of many popular acts from the genre's 1980s heyday, as well as the emergence of new, predominantly European bands, including the Darkness, Crashdïet, Reckless Love, and American bands Steel Panther and Black Veil Brides.

Musically, glam metal combines a traditional heavy metal sound with elements of hard rock and punk rock, adding pop-influenced catchy hooks and guitar riffs. Like other heavy metal songs of the 1980s (most notably thrash metal songs), they often feature shred guitar solos. They also include extensive use of harmonies, particularly in the characteristic power ballads – slow, emotional songs that gradually build to a strong finale. These were among the most commercially successful singles in the genre and opened it up to a wider audience that would otherwise not have been attracted to traditional heavy metal. Lyrical themes often deal with love and lust, with songs often directed at a particular woman.

Aesthetically glam metal draws heavily on the glam rock or glitter rock of the 1970s, often with very long backcombed hair, use of hair spray, use of make-up, gaudy clothing and accessories (chiefly consisting of tight denim or leather jeans, spandex, and headbands). The visual aspects of glam metal appealed to music television producers, particularly MTV, whose establishment coincided with the rise of the genre. Glam metal performers became infamous for their debauched lifestyles of drugs, strippers and late-night parties, which were widely covered in the tabloid press.

Sociologist Deena Weinstein points to the large number of terms used to describe more commercial forms of heavy metal, which she groups together as lite metal. These include, beside glam metal: melodic metal, false metal, poodle bands, nerf metal, pop metal or metal pop, the last of which was coined by critic Philip Bashe in 1983 to describe bands such as Van Halen and Def Leppard. AllMusic employs the umbrella term "pop metal", which refers a late-1980s variation of pop metal characterized by flashy clothing and heavy makeup influenced by glam rock (as embodied by Poison and Mötley Crüe). Use of the derogatory term "hair metal" started in the early 1990s, as grunge gained popularity at the expense of 1980s metal. In the "definitive metal family tree" of his documentary Metal: A Headbanger's Journey, anthropologist Sam Dunn differentiates pop metal, which includes bands like Def Leppard, Europe, and Whitesnake, from glam metal bands such as Mötley Crüe and Poison.

Music journalist Stephen Davis claims the influences of the style can be traced back to acts like New York Dolls, Aerosmith, KISS, Cheap Trick, Boston, Sweet and to a lesser extent Alice Cooper, were influences on the genre too. Finnish band Hanoi Rocks, heavily influenced themselves by the New York Dolls, have been credited with setting a blueprint for the look of hair metal.

Van Halen has been seen as highly influential on the movement, emerging in 1978 from the Los Angeles music scene on Sunset Strip, with a sound based around the lead guitar skills of Eddie Van Halen. He popularized a playing technique of two-handed hammer-ons and pull-offs called tapping, showcased on the song "Eruption" from the album Van Halen. This sound, and lead singer David Lee Roth's stage antics, would be highly influential on glam metal.