OK, it is scrap metal....quite a unique one for us here!
This one is difficult for me to get my head around. When you say you have a supplier and a buyer, who is who?
I mean is the supplier the one with the metal that they want to sell for scrap, or is the supplier the one actually looking for metal to buy?
The problem I am having is that most scrap metal dealers can easily be found, so people can usually go straight to them to sell their scrap for cash.
Of course that makes it pretty hard to carve out a brokerage because a broker is really only effective when they can provide deals or information that others can't find.
If you are talking about becoming a dealer, as in one that picks up from businesses and such and then delivers to the scarp yard, then that pretty straight forward.
You would need to approach businesses in your area and see if you could leave your bins there, 44 gallon drums or something, and of course have yourself a way of transporting the bins to the yard after dropping of new ones for the businesses.
Your best bet in that situation is to do a lot of door knocking to see if there are enough businesses available for you to make a business out of it for yourself.
I hope that was at least some help : )