I don’t know if they are “instrumental metal”, but Nightwish is quite good.
instrumental means not having vocals, or if you want me to slap you, not having “singing” or spoken word but other mouth noises are allowed.
metal means the music when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well.
Animals as Leaders
Though it doesn’t hold a candle to AAL, one of the first albums I remember in this specific genre is the soundtrack for Sauerbraten produced by Mark A. Pullen. Two Minute Warning
Liquid Tension Experiment