The role of the magnet is to stick to any metal containing Iron. A magnet will only stick to metal which contains Iron. A magnet wont stick to aluminium, copper, brass or stainless steel as these metals do not contain iron.
Where can I buy a magnet?
Magnets can be purchased nearly anywhere. They are used in a number of applications, so when buying one for the purpose of checking scrap metal be sure to get a strong one. Fridge magnets will work however are not suitable. The best ones to buy are ones that can be attached to a key ring… Those who don’t loose their keys wont loose their magnet.