Industrial music, in its earlier form, comprised of making
music with non-musical instruments.
Industrial metal takes this idea and furthers it, usually by
complementing metal guitars with samples, external sound effects,
and (often) heavily distorted/processed vocals.
is an acknowledged pioneer in the field, and one of its disciples,
also deserves mention as a prime influence and soundalike for many
bands in this genre.
On the somewhat more mainstream side of this genre are bands such
Nine Inch Nails