Steel is an alloy of iron that has enhanced chemical and physical properties. The most commonly found steels are alloyed with between 0.2 percent and 2.15 percent of carbon, but some steels can be found that are alloyed with other materials like tungsten, chromium, vanadium and manganese. Steel has been used since ancient times but it was produced inefficiently and expensively until the mid 19th Century, when the Bessemer process was invented. Since then, steel has been mass produced in many forms, including metal foil, plate metal and sheet metal.

Metal foil is a very thin sheet of metal that has been hammered or rolled flat. Metal foils can be made from any type of metal, although the most commonly found foils are aluminum foil and gold foil. Aluminum foil typically has a thickness of .03mm, although any sheet of metal with a thickness of less than 0.2mm is considered a foil.

Sheet metal is any metal that is thicker than a foil and thinner than 6mm, the thickness of a metal plate. Sheet metal is often used for building structures that do not require durability. It is also often corrugated or diamonded for additional strength without increasing weight. Corrugation is the creasing of the metal at regular intervals to form ridges, and diamonding is the addition of diamond ridges that add structure to the metal.

Plate metal is any sheet of metal with a thickness of 6mm or more. Plate metal is used in applications where durability is more important than saving weight. It is used in automobiles where durability is required to pass crash testing.

The only difference between sheet and plate steel is the gauge (thickness) of the metal. They both have very different uses, depending on the varying durability and weight requirements for different projects.