Some weapons have a "Frost damage" stat, but it seems to be pretty rare.
The level 13 Deithwen silver sword for example has "+19 Frost damage".
I would guess it counts as "Elemental damage", so the sword would probably just do an additional 19 points of damage, assuming the enemy has no special "Elemental damage" protection.
Is my assumption correct? Or is there some other benefit I am missing?