Blue Cheer was an American rock band that initially performed and recorded in the late 1960s and early 1970s and was sporadically active until 2009. Based in San Francisco, Blue Cheer played in a psychedelic blues rock or acid rock style. They are also credited as being some of the earliest pioneers of heavy metal, with their cover of "Summertime Blues" sometimes cited as the first in the genre. They have also been noted as influential in the development of genres as disparate as punk rock, stoner rock, doom metal, experimental rock, and grunge.

Acid rock is a loosely defined type of rock music that evolved out of the mid-1960s garage punk movement and helped launch the psychedelic subculture. While the term has sometimes been used interchangeably with "psychedelic rock", acid rock also specifically refers to a more musically intense, rawer, harder, louder, or heavier subgenre or sibling of psychedelic rock. Named after lysergic acid diethylamide (LSD), the style is generally defined by heavy, distorted guitars and often contains lyrics with drug references and long improvised jams.