Technical term is SMAW which stands for "shielded metal arc welding." This is informally known as "stick" welding or "arc" welding though other processes like MIG and TIG use an arc as well. Note that if it's "arc" welding (obviously) there'll be a blinding electric arc. If a flame or a torch is used you're probably talking about brazing or soldering, not welding. SMAW uses a consumable steel electrode which is coated with a layer of flux. The flux contains ingredients such as potassium carbonate that decompose when heated and produce a cloud of carbon dioxide gas. The CO2 gas protects the molten weld puddle from oxygen in the air. Otherwise, the steel would vigorously react with the air to produce iron oxide instead of a nice smooth weld. Technically, you *can* weld aluminum with SMAW. They *do* make electrodes designed for aluminum........ However, they produce brittle, inferior welds at best, also they create toxic, acrid fumes. They also require a lot of skill to use correctly. I've never had a reason to use these products. Other processes like MIG or TIG welding produce far better results. Aluminum is difficult to weld in any circumstances and should probably be done by professionals.