A cage is a structure of wire or metal bars in which birds or animals are kept.Mild Steel Cage Bin with Castors ; Material: MSMetal cages are used mainly to transport materials, goods, or equipment without the need to load and unload what is being carried. This saves a lot of time and considerably lowers the chances of damage. Stillages or metal cages come in a wide variety of designs and sizes and is usually made from steel or iron