Both MIG and TIG welds are types of arc welding, which utilizes the concentrated heat of an electric arc to join together metals by fusion of the parent metal by a consumable electrode. Depending on the material to be welded and the electrode used, the process utilizes either direct or alternating current for the welding arc.

The MIG weld process, or Metal Inert Gas weld, fuses the metal by heating with an arc. With this type of weld, the arc is placed between the filler metal electrode and the work piece. Shielding is provided by outwardly supplied gas or gas mixtures. A TIG weld or Tungsten Inert Gas, on the other hand, functions by joining metals through the process of heating with tungsten electrodes that do not become part of the completed weld. The process utilizes argon or other inert gas mixtures as shielding and filler metals are rarely used.

Some of the basic differences between the two types of welds are that MIG welding is faster than using TIG welding, as utilizing TIG welding requires more skill that MIG welding. A solid wire is used in the MIG Flux Cored Arc Welding-Gas Shield (FCAW-G) while TIG uses a flux cored electrode.

Another obvious difference is that TIG uses Tungsten to carry the arc, and a user of a TIG welder needs to have sufficient experience in the craft of welding. A MIG weld user, meanwhile, can carry on working despite being a novice welder.

Overall, while both MIG and TIG are gas shielded arc welding processes, the primary difference lies in the way the filler metal is added to produce the weld. With the TIG process, the arc is created between a tungsten electrode mounted in a hand-held torch and the work piece to be welded. The welder initiates the arc by means of a switch. The filler metal, in the form of a hand held rod, is then added to the weld puddle by the welder as the torch is manipulated along the joint which is to be welded. The MIG process uses a filler metal which is the electrode and the arc is created when the filler metal comes into contact with the work surface.