Metal alloys, which are a mixture of metal and at least one other substance, are used because they are more suited for a particular task than a pure metal is. Metal alloys are typically either harder, stronger, lighter or more flexible than a comparable pure metal.
Steel is an alloy made from a mixture of iron and a small amount of carbon. Steel is used to create buildings instead of pure iron because steel is much stronger and more durable. However, steel is too heavy for constructing airplanes, so an aluminum alloy called duralumin is used.
Stainless steel, commonly used in silverware and other domestic products, is created with iron, carbon and chromium. The layer of chromium oxide that forms on its surface protects it from rust. Most of the gold used in jewelry is also an alloy made from a mixture of pure gold and another metal.
Alloys are typically made by mixing a pure metal, called the main metal, with alloying agents. These alloying agents usually make up a much smaller percentage of the alloy, and they can be either metals or nonmetals. Alloys are traditionally created by heating the metal and other components until they melt and then mixing them together. Impurities in the metal are removed prior to mixing in the alloying agents.