Altered Strike

Cantrip (transmutation; enhancement, transformation, unarmed, weaponry)
Class(es): Bard, paladin, sorcerer, wizard
Casting Time: 1 Action
Range: Self
Components: V, S, M (piece of the desired material)
Duration: 1 round

You briefly transform your weapon or fist into another material and strike with it, making a melee weapon attack against a target within your reach. You use your spellcasting ability for your attack and damage rolls, and your melee weapon attack counts as if it were made with a different material for the purpose of overcoming resistance and immunity to nonmagical attacks and damage: either bone, bronze, cold iron, steel, stone, or wood.

When you reach 5th level, you can choose silver or mithral as the material.