I have used mild, "Cor-Ten", stainless steels as well as bronze (sheet metal) in a distinctive way. The result is a configuration of planes bordered (connected) by welds. The best examples of this are Earth Woman, Gambrinus, King of Beer and Bicentennial Monument. Instead of grinding off the welds, I let them become an arrangement of lines with a life of there own. If you removed the sheet metal and only the welds remained, you would have a "line drawing" which would (I think) describe the form.
On very large works like the Eagle Sculpture Landmark, I have interior structural steel but the outside; i.e., for what you see, I use the following few pieces of equipment: an oxygen and acetylene welding torch, a (Stanley) nibbler type shears (which I bought in 1962) and a 3 roller hand cranked metal roller which can be used to both straighten and curve the sheet metal. The metal thickness that I use the most often is 16-gage.
Usually I will make a model out of Roma Plastilina (oil based "clay"). I form the planes in that model. Next, I trace, the shape of each plane on clear plastic. Using an over head projector, I enlarge the shape to the desired scale on card board and trace it on to the sheet metal, cut the metal with the shears and then curve the plane if necessary. I then tack the pieces together, refine the form and then try to get the best welds that I can. When the viewer observes the linear pattern of the welds, I would rather not have lumps or "chewing gum" welds stop the journey.