Manganese is chemical element 25 on the periodic table. Its symbol is Mn. (Some people get it confused with magnesium, the symbol is Mg). Manganese is used a lot in steel to make it stronger. This is the main use for manganese metal. Manganese compounds, particularly manganese(IV) oxide, are used in alkaline cells and Leclanche cells. Manganese metal is also alloyed with aluminium.