Bronze is used for spying out other villages. In order to successfully spy out a village you will have to send more bronze than the amount which is stored in the according habitat.
For instance: should there be 8000 bronze in the habitat which is to be spied at, you will have to send 8001 bronze, only in this case your spy will return with a report. Also the according player being spied at will not be notified. Should you be sending 7999 bronze, your spy will be captured, this will cost the other player 7999 bronze. He will however be notified about this.
You can barter bronze for resources within the marketplace, the higher the level, the better the exchange rate.
For instance: should there be 8000 bronze in the habitat which is to be spied at, you will have to send 8001 bronze, only in this case your spy will return with a report. Also the according player being spied at will not be notified. Should you be sending 7999 bronze, your spy will be captured, this will cost the other player 7999 bronze. He will however be notified about this.
You can barter bronze for resources within the marketplace, the higher the level, the better the exchange rate.