There is a PnP RPG that has living metal in it (I was referring to them in my first post, not the Wall-E type things), and they don't really care. They don't feel pain, so the forging doesn't hurt them, and since the smiths can only make that out of the metal which it wants to become (a sword in our case), it'll even be happy and easier to forge. Apart from that they don't care for what they are used, but the wielder needs to be respectful towards them, or they'll get her killed.