how would he use his investment in copper to survive?
There is many question here and i think you have the wrong one. Precious Metal are a way to protect wealth, not survive and you need to actually have wealth.
You are better to get seeds and start a hidden garden, get rabbit or chicken, solar panel and water filtration if your goal is to survive. These are the right tools for the job, precious metal aren't. Build a community around yourself by moving away from city, then only trade with farmer that are in a walking distance of where you live.
When you have all you need to survive and paid without debt and you have wealth left (or you have wealth left and you ran out of time to get prepared), then you can use precious metal to store your wealth and recover it after the crisis.
OR
You can use precious metal to temporarily store wealth and make some, while they are worth more than face value, and spend it before the crisis arrive. Like hoarding metal at half it's price right now, wait for them to double in the next 2 years and buy a land before the society fell apart.
When there is no food in sight i think precious metal will be almost throw away, it will be a good time to trade them for a little food if you are really WEALTHY. Good time to buy and get richer, bad time for desperate seller who only have precious metal.
No one know the future, but if the crisis happen gradually, slowly over time, even poor people have time right now to store precious metal, in 2-3 years it will have grow big enough to buy a land. If the crisis happen very fast and sooner than you expected, precious metal will be only useful in like 10-15 years after the crisis, when industrial will have recover and start producing again.
Precious metal may be able to buy a land after the crisis has happen, to a desperate soul ready to sell all his life investment and flee in another country. You can't carry 6 month of food on yourself but you surely can move some ounce of gold. They may also be able to buy your life at the hand of a corrupt cops or military, where gun is useless since they will always out gun you. But from what i read, a bottle of liquor or cartoon of cigarette does a better job to grease the wheel in these situation.
I'm not sure of anything i written here. But each month i get deeper and deeper into the subject, my opinion of survival and precious metal change, it's obliviously a good move but exactly how it is and what's it's for get transform as i understand better and get my emotions around the idea that life in the future isn't going to be what i'm used too in the past.
This is my opinion and in no way a absolute truth. I have no idea if it's right or not. I currently being anxious every now and then that i'm wrong and never sure of what to do. I tweak my point of view every month about what's going on in the world and how i should react. So far i think this is the safest and best path for me.