Avant garde metal, sometimes called experimental, is a cross-genre reference to metal bands characterized by large amounts of experimentation and by non-standard sounds, instruments, and song structures. While progressive metal, like avant garde metal, is also a genre which favours experimentation and non-standard ideas, there are rather large differences between the two forms. One of the most striking differences is that the experimentation of progressive metal lies mostly in complex rhythms and song structures, while the genre usually sticks to a more traditional instrumentation, whereas in avant garde metal the usage of unusual sounds plays usually a fundamental role. Most of the artists that play avant garde metal also have a strong focus on a generally dark atmosphere. The bands involved have often been associated with black metal, and a number of avant garde bands also have a black metal background, but it is generally looked down upon by black metal purists, who consider common elements from avant garde metal, such as keyboards or female vocals, an alienating element which has nothing to do with "real" black metal.
It should be noted that there is no common agreement within the metal world on the correct usage of the term avant garde metal, though certain issues, such as the presence of experimentation, are agreed upon.