Self-drilling screws have their own drill point that bores a hole and proceeds to cut its owns mating threads — no need to drill a pilot hole. Use these screws to attach thin pieces of metal to a metal or wood frame.
Use stainless steel self-drilling screws for applications where you need extra corrosion resistance. Made from type 410 stainless steel, these screws are heat-treated and hardened to drill more effectively. They are sturdier than screws made of other grades of stainless.
However, even type 410 stainless has its limitations. When you need extra protection, look to Marutex. Marutex self-drilling screws are specially formulated with 2% molybdenum (the same element that gives type 316 stainless steel its salt water corrosion resistance). When corrosion is a concern, Marutex screws offer superior protection over regular 410 stainless steel.