I was just wondering if there is a platform for trading precious metals? Something similar to a FOREX platform.

Answer
Depends in part on what you mean when you say trading precious metals. If you are referring to buying futures contracts, yes, most brokers allow you to buy precious metals - however, these contracts are usually cash settled for convenience, so you don't receive possession of metal when they expire.

If you wish to take physical delivery, you need to trade something like the NYSE Liffe precious metal contracts - just be forewarned that even the mini contracts are still rather sizeable - for example gold is a 33 oz bar, so will set you back over $34,000 today. Most brokers will still try to cash settle, then next to deliver a certificate, and have to be instructed to give you physical delivery, which they don't really want to do.

You will be able to get 'wholesale' price in effect, as the futures contract allows you to cut out the middlemen like bullion dealers, etc..

What do commodities traders do? What is their role in the stock market?

Do the traders have anything to do with setting the price of the commodity?

Answer
Commodity traders buy and sell commodity instruments such as coffee, sugar, gold, silver, crude oil, wheat. Teir role in the stock market is to act as intermediaries between the buyer and seller. I am a forex trader, so my buyer/seller is clients and/or Citigroup. The same goes with commodity trader. Yes, traders have and always will have a huge factor in setting prices.