Store metal items (Metal caps of bottles, aluminium and steel cans, bits of iron, steel fittings, sanitary fittings, parts of vehicles, lighting fixtures) in a container. Copper which is present in electrical wires can also be stored in the same box. The recycle guru will sort these at his shop. Keep aluminum foil used for storing food separately, this foil often found in take away containers can be recycled even if it has a bit of food on it. Best to rinse and store since it is easier to handle and won't smell.
Like glass, a pure piece of steel can be recycled again and again. However, steel is often mixed with other metals to make “alloys” or even other materials like plastic, which makes recycling much more challenging. In the recycling process, metal only has to be melted down in order to be used again in a new form. Definitely more energy efficient than extracting new metals from the earth!