I would like to know if my understanding of the futures market is correct. Firstly, only producers of commodities can sell short and can buy a short positions; while anyone can buy long. Secondly, either one of the parties have to pay a margin for the loss they have suffered daily to the risk of losing their position, and a margin deposit initially as well as a certain percentage of contract value. Thirdly, transactions have to be made with the commodity that was traded or fiat currency. Fourthly, if either the suppliers or the buyers default massively unable to pay in the commodity that was traded or in fiat currency, the future market will likely crash, which is the reason why there was concern over the COMEX in recent weeks. Correct me if I am wrong, please.