Principle
Only the metals iron, nickel and cobalt are attracted to magnets. Iron is significant for the production of steel. Steel is an alloy of iron and various other elements added according to the desired property.
Nickel shines silvery-white and is used in coins and as a coating for other metals because of its durability. Cobalt, of which no sample is included in the set, is a very hard metal of blue-gray color. As an alloying component in steel, it makes it more wear resistant.