Performing a Copper Crown involves three parties: the Giver, the Receiver, and the Enabler. Traditionally, the Receiver is a male, the Giver can be any gender, and the Enabler must be a menstruating female. The Giver starts off by performing cunnilingus on the menstruating Enabler, resulting an copious amounts of blood in, on and around the Giver's mouth. The Giver then "crowns" the head of the Receiver's penis by kissing it, leaving a ring of blood around it.
It is theoretically possible for a Copper Crown to be performed with only two people, provided that one person is either a female flexible enough to be both the Giver and the Enabler, or a menstruating hermaphrodite.
The name comes from the coppery tastes of the blood left in the Giver's mouth, and the ring of blood being left around the head of the Receiver's penis, much like a crown.
B: "Well, her mom walked in on us having sex ..."
A: "Oh man! That's one way to ruin the mood."
B: "Actually, she joined in and it ended with me getting a Copper Crown!"
A" " ... that is seriously fucked up, dude."