Most metals found in the earth's crust are part of oxide compoundss. Metal-oxide compounds must be reduced to liberate the desired metal. There are two methods of reduction, electrical and chemical. Electrical or electrolytic reduction involves passing a large current through a molten metal oxide or molten metal oxide solution. This is how aluminum and many other metals are reduced. Chemical reduction makes use of a chemical reducing agent to change the oxidation state of the metal. In the case of iron, this reducing agent is coke. Coke is carbon. When coke is mixed with iron oxide and heated, the oxygen will move from the iron to the carbon. The iron will be reduced, and the carbon will be oxidised, producing carbon dioxide and carbon monoxide.