Sheet metal screws have a pointed end and widely spaced threads. They're self-starting in thin sheet metal, but in thicker materials a drilled hole is recommended.

Stainless steels are used for their corrosion resistance, high-temperature strength, scaling resistance, and low-temperature toughness.  These properties account for their extremely wide use in practically every industry. Austenitic Stainless Steels are alloys of iron and carbon that contain between 16% and 30% Chromium, a maximum of 0.15% carbon, along with Nickel (or Manganese), and other alloying elements.  The chromium, which helps develop a passive surface oxide film, provides corrosion resistance in stainless steels.   Austenitic Stainless Steels are designated by a 3 digit SAE Stainless Steel Grade beginning with the number 3 (e.g. 304, 316).  Another common naming convention for Austenitic Stainless Steels are 18/8, 18/10, 18/0, etc. where the 18 refers to the % of Chromium and 8 to the % of Nickel contained in the material.    

Similar to a flat-head style, the oval head style has a slightly convex top surface; it is typically used for appearance. The Phillips drive style was originally designed so that the driver would slip out under extreme torque, preventing over-tightening and damage to the fastener or the material.