There are at least two artists/bands that go by this name:

1) Loon (born Chauncey Hawkins November,4 1975 in Harlem, New York) is an African American rapper formerly part of P. Diddy's Bad Boy Records, where he released his self-titled debut album, Loon. He has also made many guest appearances on songs of the R&B and hip hop genres. In 2004, Loon left Bad Boy to start his own label, Boss Up Entertainment. Loon started his music career as a member of Mase (Mason Betha) rap collective Harlem World.

2) Three-piece doom metal band from Providence, RI, featuring members of Megasus, Moonshine, and Wake Up On Fire. Loon alternately plays slow and driving sludge/doom with tortured, strangled vocals, and a more mellow, melodic variety of metal with clean vocals and the occasional dose of acoustic folk thrown in. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.