The History of Olympic Medals
The Olympic Games is an ancient tradition, dating back to the Greek Olympiads of 776 B.C. However, the history of Olympic medals is not quite as old - the first Olympic games to actually use medals as prizes was the games of 1896, where the winners received silver, and the runner-up bronze. Before that, in the ancient Greek's games, the prizes consisted of simple olive wreaths, which were considered the highest honor one could receive.
Olympic Medals Through the Ages
As mentioned, the first appearance of Olympic medals were in the first modern games of 1896. Since then, the medals have not stayed the same, but have differed a lot in size, looks and even material. Every game has had its own unique medal design, ranging from squares, to donut shapes, to weird looking blobs.
The only thing that has shifted more than the design is the material of the medals, which weren't always gold, silver and bronze. In one year's Olympic games, the medals were actually made up almost entirely of glass. And in the 1900 games in Paris, they even replaced the medals with various other prizes for the winners - for instance, one runner-up pole-vaulter won an umbrella. It was only in 1904 that the standard awards were assigned as gold, silver and bronze.
Today's gold medals aren't even made entirely of gold, but are merely gold plated silver.
Meaning Behind the Medals
As previously mentioned, the ancient Greek Olympics didn't award medals to the victors, but olive wreaths instead. This wasn't because they didn't have fancy metals to make medals from back then - quite the contrary! The reason they had a simple olive wreath as award was because the ancient Greeks believed that fighting for honor was a much more noble cause than fighting for possession. As a symbol of this, nothing of actual value was ever handed out as awards in their games - only honor could be won.
Since the start of the modern Olympic games however, the awards have always had material value, and have a completely different meaning than in the ancient games. Somewhat inspired by the Greeks, the modern games award medals based on the three Ages of Man from Greek mythology. The gold medal symbolizes the Golden Age, when men lived among the gods, the silver medal symbolizes the Silver Age, when youth lasted a hundred years, and the bronze medal symbolizes the Bronze Age, which was the era of heroes.
So although the awards as well as the motives behind them have changed through the history, at least some part of the Greek heritage remains in them - even though it's an entirely unrelated part of their culture.