Isis was an American post-metal band formed in Boston, Massachusetts in 1997 by guitarist and vocalist Aaron Turner, bassist Jeff Caxide, vocalist and electronic instrumentalist Chris Mereschuk and drummer Aaron Harris. After a demo and the EP Mosquito Control were recorded by the original lineup, Mereschuk was replaced by Jay Randall in 1999, who joined the group alongside guitarist Michael Gallagher. Jay Randall would later be replaced by guitarist and keyboardist Bryant Clifford Meyer after the recording of Red Sea. With roots in hardcore punk and doom metal, the band borrowed from and helped to evolve the post-metal sound pioneered by bands such as Neurosis and Godflesh, characterized by lengthy songs focusing on repetition and evolution of structure. Isis disbanded in June 2010, just before the release of a split EP with the Melvins, reforming only once in 2018 as Celestial for a one-off show to pay tribute to Caleb Scofield.

Post-metal is a music genre rooted in heavy metal but exploring approaches beyond metal conventions while being related to and similar to post-rock. It emerged in the 1990s with bands such as Neurosis and Godflesh, who transformed metal texture through experimental composition. In a way similar to the predecessor genres post-rock and post-hardcore, post-metal offsets the darkness and intensity of extreme metal with an emphasis on atmosphere, emotion, and even "revelation", developing an expansive but introspective sound variously imbued with elements of ambient, noise, psychedelic, progressive, and classical music, and often shoegaze and art rock. Songs are typically long, with loose and layered structures that discard the verse–chorus form in favor of crescendos and repeating themes. The sound centres on guitars and drums, while any vocals are often but not always screamed or growled and resemble an additional instrument.