Before everyone jumps the gun and say they can .. let me clear up what I mean by CANNOT BE UPGRADED I don't mean the items listed below aren't ABLE to be upgraded, I'm saying they cannot be upgraded because there are no instructions on HOW.
1. The Drag and drop doesn't work for a Wetstone, an Anvil, and a Furnaces like you do everything else in this game.
2. Other than a Wetstone, an Anvil, and a Furnace, there is no place in the game that I can find that you can drag and drop these items into which is how you upgrade metal weapons and armors.
3. There are also no instructions anywhere (Including the crafting guide on this site) that explain HOW TO UPGRADE any of these item types. It doesn't matter if you know what ingredients you need to upgrade an item if you're never explained how to use those ingredients in order to get the item upgraded.
HERE IS THE LIST OF ITEM TYPES THAT NEED INSTRUCTIONS FOR UPGRADING:
Any leather items
Any Cloth items (Robes, hoods, belts and such)
Any wood items Such as Shields and clubs and Staffs
Any Rings, and amulets
So yeah as it stands now the items on the list above cannot be upgraded because there are no instructions on how to get them upgraded.