The first important step before bringing your metals to a scrap yard is to determine if they are ferrous or non-ferrous and separating them, to get the full value for your materials.

The easiest way to find this out is by using a magnet, any magnet will do, even a fridge magnet. 

If the magnet sticks to your metals, these are ferrous metals and most commonly include steel or iron.  Ferrous metals are less valuable and you should separate them from other non-ferrous metals when scrapping.

If the magnet does not stick to your metals, these are non-ferrous, and will commonly include aluminum, stainless steel, copper and brass.  Non-ferrous metals are valuable, usually sold by the weight at your local scrap yard.