Store of value
Gold coins and bars are a good form in which to hold some of our wealth.
At any time one wishes to convert them into cash, all one has to do is to go to the local jeweller and receive the then prevailing price in return for the gold.
Of course, the price can fluctuate, but given that gold is a scarce resource in the world, one can be sure that one will get some value for this at all times.
Also See: What should you know before investing in gold