If we’re trading gold and silver, then we have a monetary system, not a strict barter economy. The definition of money is, “A medium of exchange, or a store of value,” independent of the item’s practical use. Gold and silver have some practical uses, but those will be no more relevant in a total economic collapse situation than will be the decorative value of cowrie shell.
2 things I can think of regarding metals after the SHTF: First Gold/Silver will be easily, (and maybe the only thing), accepted by any new Gov. of ours that comes out of the ashes as a conversion or ‘trade in for the new’ for what they possibly might or will establish as their new ‘money’ system. 2: Their might be folks whom will only accept for whatever their reasons, as a trade for their goods/items etc, precious metals from the second party. We will see I guess.
The concept of money does not require government.