Most metals in everyday use are alloys, which are mixtures of a metal with other elements. Bronze is an alloy of copper and tin and is used for statues and medals. Brass is an alloy of copper and zinc and is used for door fittings and musical instruments. Gold used for jewellery is usually an alloy with silver, copper and zinc. The proportion of gold is measured in carats. 24 carat is pure gold, which is 100% gold, so the percentage of gold is the carat number divided by 24, multiplied by 100. 18 carat gold is 75% gold, and 12 carat gold is 50% gold.
Steels are alloys of iron that contain specific amounts of carbon and sometimes other metals. High carbon steel is strong but brittle, and is used for cutting tools. Low carbon steel is softer and more easily shaped, and is used for car bodies. Steels that contain chromium and nickel are called stainless steels. They are hard and resistant to corrosion, so they are used for cutlery and sinks.
Aluminium alloys have a low density, so they are used where a strong but light metal is needed, such as in aircraft.