Why are coins made from metals?

Answer 1

To make them harder to copy, prevent them from catching fire or being bent or snapped, etc.

More completely and correctlyCoins were originally made from metals whose value was the same as the coins' denominations. That meant that a penny contained a penny's worth of metal (sometimes copper, sometimes bronze, etc.), a shilling contained a shilling's worth of silver, and so on. That gave the coins a fixed measure of worth so that everyone would accept them as a medium of exchange.

As economies developed, other reasons were found. Metals last a long time, so the life-cycle cost of making a coin was less than that of paper money at least for smaller denominations. They're also convenient, and with the development of machinery like coin counters and vending boxes the use of metal instead of other materials proved particularly useful. For example, modern vending machines use electronics to determine the composition of a coin before accepting it; that's much more difficult with paper bills that could have different images, be worn or torn, etc.

However coins don't always have to be made of metal. In fact, at times some countries have used everything from leather to pottery to make coins. As new materials such as metallised plastics and nonbrittle ceramics are developed, it's quite possible they could be used for coins as well.