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
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.
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.
The reasoning is that precious metals ... Especially gold and silver ... Have been a valid form of currency for thousands of years. And barter wouldn't necessarily work after an economic collapse.
Person A has food. Person B has food and clothing. Person C has spices. Person A wants spices, but Person C wants clothing. Person B doesn't need Person A's food. So Person A needs some other form of "currency" to trade for the clothing or spices ... Such as gold.