To begin, DO NOT TRY THIS SHIT AT HOME. It’s incredibly dangerous, and although the linked video is an excellent primer for the concepts involved, it totally glosses over safety issues. One of the potential dangers, I understand, is that moisture in the smelted metal may cause a small pop, sending LIQUID HOT METAL FLYING ALL OVER YOU. So you’ve been warned.
But with that said, here we have James May from the Man Lab demonstrating the basic principles of building a small smelter and using the ancient technique of metal casting to make something useful. I have to say I find the process rather beautiful, in an insanely dangerous kind of way.