As the lovechild of R&B and country, it's no surprise that rock music has spawned a number of its own subgenres from metal to new wave to alternative and powerpop. Of all these, heavy metal has come to typify all that is truly "rock." Signified by guitar-heavy riffs (and the occasional sugarsweet ballad), this genre has had a loyal following since the mid to late 1970s. In the mid-'80s, heavy metal became highly commercialized (and hairsprayed), as bands such as Poision and Def Leppard mastered the art of combining slamming guitar licks with Top 40-style hooks. As "hair metal" became something of a joke, harder-sounding bands like Guns N Roses and Metallica took center stage, redefining rock music yet again.
Another result of the excess of the hair band phenomenon was the emergence of grunge rock. Grunge bands such as Pearl Jam, Soundgarden, Stone Temple Pilots, and Nirvana (arguably the most influential) rebelled against the typical rocker image of long hair, tight pants, and flashy stage performances. This generation of rockers instead made their mark on the music video format. Videos such as Nirvana's "Smells Like Teen Spirit" and Soundgarden's "Black Hole Sun" typify the dark imagery of the genre.
As grunge faded into alternative in the mid-'90s, female acts were more readily accepted in rock music. Alternative divas Tori Amos and Alanis Morissette both left marks in the industry for their uncompromisingly feminine lyrics. As the headiness of grunge diminished, mainstream rock also began to take on a more pop-like sound. Punk bands such as Green Day and Blink-182 combined driving guitar riffs with upbeat melodies, much in the same manner as so-called hair bands did in the '80s. As the rock music genre came full circle, though, powerpop bands maintained a strict tongue-in-cheek attitude.