NPR’s Planet Money has a nice story on why gold is used for money. They take the entire periodic table of elements and eliminate the ones that don’t work because they’re too reactive, a gas, too common, or too toxic. You’re left with five precious metals, rhodium, palladium, silver, platinum and gold, but only one of them has a low enough melting temperature so that it can be worked easily and is not ridiculously rare.
Also, Tony Clayton has a wonderful webpage on Metals Used in Coins and Medals. It has some fascinating details about the history of these metals and their alloys in coinage. For example, “In Old English the Latin word aes was rendered as brass, thus the use of the word brass to mean money still found today, especially in Northern England. “