Mettin is one of Kirkwall's Templars.
Ser Mettin is involved in the quest "The Last Holdouts" where both He and Ser Agatha enlists the aid of Hawke in dealing with citizens harboring apostates. Unlike Ser Agatha, He holds extreme views about his duties. If Hawke chooses to side with Agatha regarding on how to deal with the mage sympathizers, Hawke will be forced to kill Mettin. Otherwise, Hawke will fight Agatha alongside Ser Mettin.