Copper is a broad category that includes varying alloys of copper with other metals. Aurigan is an example of one copper alloy available under a specific brand name. “German Silver”, despite the name, is also a copper alloy using copper, zinc, and nickel.
German Silver is very commonly used in dressage bits, and tastes sweet to improve salivation. German Silver bits are generally in the mid to high range for cost, with reasonable durability.
“Kangaroo Metal” is another type of nickel/copper alloy with the same sweet taste characteristics. It has a dull finish, and tends to be expensive with poor durability.
Straight copper bits are generally used only in mouth pieces with separate steel rings due to the low strength of pure copper. Warms quickly, but along with the low strength you will see low durability.
Copper bits generally have a desirable sweet taste for your horse.