With 3, Dream Theater, and Between the Buried and Me. Saturday, May 17, at Time Warner Cable Amphitheater at Tower City.

There's really no such thing as a casual Opeth fan. It takes a long attention span and an open mind to fully appreciate the brilliance of the world's best death-metal and progressive rock band. These fearlessly original Swedish longhairs win diehards by catering to charismatic frontman Mikael Akerfeldt's boundless vision. In an age when music is consumed instead of listened to, Opeth treats its albums as singular artistic statements, composed of interlocking songs with recurring themes and incredible musicianship. The group exchanges traditional song structures for "movements" that often stretch past the 10-minute mark and feature extended instrumental passages. Akerfeldt's longtime affection for psychedelic rock, folk music, and obscure '70s prog informs his songwriting, making Opeth one of the few extreme metal bands challenging heshers to appreciate more mellow genres. Despite its complexity, Opeth is starting to receive the mainstream recognition it deserves. Its last album, 2005's Ghost Reveries, was the band's biggest seller. This week's concert will focus on the new Watershed, which drops next month.