Vikings did not play "metal". They were strictly acoustic musicians. Their favorite instrument was Frenchmen, which they played by whacking them with swords until they emitted loud bleating sounds.
It was said that a squad of Vikings could produce interesting harmonies by this method, but unfortunately the music didn't last too long.
When the Vikings invaded Britain, they found a new source of tunes which they performed by sticking spears into the natives.
However, eventually they all settled down and became Beatles.
KILL YOUR TV