Time to learn some terminology. MIG stands for Metal Inert Gas. This type of welding is when the gun uses a piece of wire connected to an electrode current and inert (unreactive, nonoxidizing) gas to connect two pieces of metal together. Argon is the most common inert gas used. TIG stands for Tungsten Inert Gas and uses Tungsten attached to an electrode current and inert gas to join the metal. In these processes, the wire in MIG welding is incorporated into the metal, while the tungsten in TIG welding is not.