Family Tree: Led Zeppelin

Led Zeppelin may be the embodiment of heavy metal, but the branches of their family tree reach far beyond banshee screams and mountainous riffs. The foursome's many former bands, side-projects, and session credits encompass not just rock ‘n' roll, but folk and psychedelia as well. Then there's Robert Plant's solo career, which is nothing less than a compendium of 20th-century musical forms.