Numerous bands have made attempts in this vein. It almost always ends up being shit, because either 1) there's a failure on the bands' part to realize that metal is a fully Western form of music and cannot truly be incorporated into other cultural musics without an acknowledgment of that fact, or 2) more often, the ethnic instrumentation is little more than a gimmick.
I do remember reading an old text file somewhere on ANUS about a metal band incorporating Native American music. It interested me, but I was never able to find anywhere to download the music. The band wasn't even listed on M-A, from what I recall.