I know for years that food, wood and gold were always the standard resources, which I believe is good enough for the most part. However, it bothers me of the lack of metal they could use. What if oil known as black gold be a late game resource if they decide to add tanks to the game. Could there be a better way to name our resources so that we would not have to add any more to the game? Should we just stick with what we have?
I also had a weird idea that each civilization has their own unique resources that they can trade with one another that would give special discounts on buildings or units or simply just be used for upgrades to certain units. Another weird idea is oil derricks bringing bonuses to units that use it and it would also generate gold for resources.
Anyways, metal is pretty much a resource only found in mines. They are mainly used in artillery, tanks and the early game units use it. You can also settlers to harvest gold from rivers like they did in the yukon and so forth. Gold would be something you acquire through trade and there would be additional ways of getting it. (Special gold mines, trade through the market, settlers harvesting gold from the rivers like they did during the gold rush.