It can sometimes be difficult to decide which sort of metal something has been made from and if you want to separate metal objects into different types such as steel and aluminium a magnet can make identifying and sorting metals a whole lot easier.

A small magnet will stick to steel objects but have no effect on aluminium so a magnet makes it a whole lot simpler to sort out the steel cans and scrap from the aluminium and since aluminium is usually worth more money it can be worthwhile separating the two metals.