Metal is made from metal ore which has to be mined, refined and processed before it can be used. Metals are available in a wdie range of sizes and shapes so not much work has to be done to change their form. It is rare for metal to be used in it's pure form. They are normally a mixture of two metals. A mixture of two metals is an alloy and metals are alloyed to improve their properties. Metals are either ferrous (containing iron) or non-ferrous (not containing iron). Both of these can be recycled.
Pure iron is usually to soft for most things so it can be mixed with other metals to make it stronger, for example carbon to make carbon steel. Carbon steel is one of the most used metals in the world and most carbon steels have poor corrosion resistance so they can rust easily. To prevent rusting they can be coated with other metals that are resistant to rusting like zinc. The amount of carbon added affects the properties of the metal.
Low Carbon Steel - This is the weakest steel, it is easy to machine, tough and cheap but cannot be hardened.
Medium Carbon Steel - Strong, tough, hard and quite cheap but can't be hardened.
High Carbon Steel - Stronger and harder than MCS but not as tough and hard to form although it is quite cheap and can be hardened.
Aluminium - Lower density than steel, high corrosion resistance, more expensive than steel and not as strong, often alloyed to improve properties.
Titanium - Stronger than aluminium, excellent corrosion resistance, lower density than steel but more expensive.
Zinc - Low melting point (so ideal for die casting), can be alloyed with aluminium and this increases it's strength.
Copper - Good conductor of electricity, flexible, lack strength, alloyed with copper oxide to add strength.
Bronze (alloy of copper and tin) and Brass (alloy of copper and zinc) - Bronze is often used for casting whereas brass is hard to cast but can be machined to create a good surface finish.
Key Terms and Tips
Alloy - A mixture of two metals
Ferrous Metal - A metal that contains iron
Non-Ferrous Metal - A metal that does not contain iron
When discussing the selection of metals, make sure that you describe the most important properties for the context, for example if you were describing aircraft construction you would describe weight and strength.