Specifically they both have their advantages and disadvantages. With TIG welding, one can perform a variety of weld types on several different metals. Steel and aluminum, however, are the two most widely used metals. The filler rod is another important aspect of TIG welding. Usually made from the same material as the base metal, it is used for reinforcing joints and welding heavy metals. There are several different types of joints designed for use with TIG welding. These include the butt joint, lap joint, corner joint and t-joint. The butt joint can be welded without the assistance of a filler rod. With this type of joint, two pieces of metal are joined together along the seams. The primary advantage of MIG welding is that it allows metal to be welded much quicker than traditional welding "stick welding" techniques. This makes it ideal for welding softer metals such as aluminum. When MIG welding was first developed, the cost of the inert gas (i.e., argon) made the process too expensive for welding steel. However, over the years, the MIG welding process has evolved and semi inert gases such as carbon dioxide can now be used to provide the shielding function which makes MIG welding cost effective for welding steel.