Welding is the process of joining metal together structurally. For a fantastic instructable that is a very in-depth look at the theory, details and safety about MIG welding, read noahw's How to Weld - MIG Welding
This instructable is focused on the steps to perform regarding the equipment for welding. It assumes that the machine has enough air, the wire is threaded and that all safety is accounted for. It also assumes you have set up your components to weld.
I made this at TechShop Detroit (www.techshop.ws).