Avant-Garde/Experimental Metal

A subgenre of heavy metal music loosely defined by use of experimentation and characterized by the use of innovative, avant-garde elements, large-scale experimentation, and the use of non-standard and unconventional sounds, instruments, song structures, playing styles, and vocal techniques. It evolved out of progressive rock, jazz fusion, and extreme metal, particularly death metal and black metal. Experimental metal also uses unusual sounds, breaks conventions, and often includes new elements. The lyrics and visual presentation of the genre are eclectic as well.

Source: http://en.wikipedia.org/wiki/Experimental_metal