Does the wire size make any difference as it relates to the thickness of the steel. I am building a truck and working on the body, 16 ga and the frame parts 1/8" thick.

Hi, my name is Marten. New to welding for sure. Bought a project truck a couple of years ago and building it into my dream. Thought I should learn to weld so I can do the work myself. Learning and was told of this web site, so here I am. Wanted to put a picture of it my avatar but says my picture is...