I am thinking of trading Futures, more specifically the ES - Mini S&P 500 and I have a question. The Initial Margin for this contract is $5625. Now suppose I have $7000 in my account I buy one contract at 1100. Overnight something terrible happens and the S&P 500 opens at 800 and never goes about 800 the whole day. So I have lost 300 points at $50 each = $15,000. So what is my liability? Is it just the margin of $5625? Or the actual amount of $15,000? I assume that my position would be immeadately liquidated at the open, correct? If I am liable for the full $15,000 and my account only has $7,000, what happens to the rest of the $8,000? If had some other stocks worth say another $2000, could they sell those too? Can they sue me for the rest???