Sara Lewis answered The inner and outer cores are both made up of over 90% metal. In fact, the earth is made up of four layers, all with very different properties, and made up of different materials.The layers are as follows:The Crust. This is the outer layer, and the only one we can physically see. The Mantle. The widest section of the Earth made up of semi-molten rock known as Magma.The Outer Core. A liquid layer made or iron and nickle.The Inner Core. The centre of the earth. It is also made up of iron and nickel, although in solid form.Therefore the only two layers that are made mostly of metal are the inner and outer cores.It is thought that the core as a whole is made up of 80% iron, with the other 20% being predominantly nickel, with traces of other less dense metals which are difficult to measure.