You're using the wrong tool for the job. Try Gresham's Law instead.
Gold isn't used as money because there is shittier money being accepted.

To the OP; you are correct that Gold is not an investment. Investments are basically gambles with the intent that the return is far greater than the initial loss. Gold doesn't function that way (with some small temporary exceptions). It is however, a store of purchasing power. The idea being one can lock up excess funds into Gold and then when those funds are needed they still buy the same amount of goods and services regardless of which direction the original currency went in the meantime.

Finally, to the poor sap who can't buy or sell metal without losing his ass; it isn't the metals that suck it is you who sucks at moving in and out of metals.