Bronze is an alloy of copper and tin and was extremely important to the development of civilizations several thousand years ago. The third phase of Man's development was indeed named the Bronze Age and as early as 3000BC bronze was being made.

Tougher than copper, bronze is easily melted and cast and is less susceptible to corrosion. By altering the proportions of the alloys (largely copper and tin) you can create very different types of bronze used for very different purposes. Statutory bronze may have less than 10% tin but the bronze used to make bell metal can have as much as 25% tin and creates the tone when struck that gives it its name. Similarly, bronze used in weapons, such as swords might have zinc added to the alloy to give extra strength. Manganese and phosphor also improve the strength of bronze. Even by medieval times, specific proportions were understood to create these different results.
Silver and bronze ring with moonstone by Hannah Warner