What use would gold, silver, and other metals be if there was a collapse? A few people suggested it for the "end times" scenario or the collapse of the USA. But I don't see why anyone would trade food or other necessities for a piece of metal.

Gold is what backs our currency up currently so if the US dollar falls, then gold and silver will be the only currency recognized anywhere in the world. But gold isn't a lightweight metal to be carrying around and for awhile it'll be mad in the world with people killing and stealing and robbing for whatever they want

You would be correct. Gold and silver are not the valid currency anyway, human labour is. This is why money is a paper IOU.  A bank loan is not a loan of money but IOU (credit). The bank checks your assets then promises to pay you an IOU which you pay back with interest. It is a debt and discharge system.

So yes food would be the most valid commodity just like it was in the beginning. Whenever there is a surplus amount of food, there is the ability to control that food and so gain power.