FARMINGTON, N.M. — Edmund Yazzie is not the type of guy you expect to see at a heavy metal concert. He is 46, well past the age of youthful angst. As a veteran lawmaker on the Navajo reservation, he is also an integral part of the establishment, known for his starched shirts, polite manner and ardent anti-marijuana stance.

Nevertheless, on a recent Saturday, Mr. Yazzie was at a metal show in this small city, standing in a throng of headbangers as a man in black roared into the microphone. But Mr. Yazzie was not there to court voters or counsel against drug use.

He was there to play.

In the small world of Navajo “Rez Metal,” a cluster of rock bands that perform on and around the tribe’s reservation, Mr. Yazzie is not only a participant, but a leader, hosting concerts on his family’s ranch and touring the region with the four-man band he helped start in 2011, Testify.

Although Testify sometimes performs with other bands that have the defiant-sounding names associated with the genre — Skull Fist, Abysmal Dawn and Night Demon, for instance — the message of Testify’s songs is uplifting: Titles include “Move On” and “Live for Something, Die for Nothing.”