Aluminium and Titanium are two metals with a low density which means they are lightweight for their size. Aluminium is used for aircraft, trains, overhead power cables, saucepans and cooking foil. The metal burns in air and is the only element that burns in nitrogen. It is marvellous in fireworks. Aluminium and Titanium resist corrosion as they have a very thin layer of their oxides on the surface, which stops air and water getting to the metal.