Lets say we have 3 devices in the same shared medium : A, B and C.
A wants to send a message to B, so before, it sends an ARP request as a broadcast message. When B receives it, it will update its ARP table with A's MAC address and send a unicast response. C also saw A's broadcast message, so it could also add A's MAC address.
Therefore, I think that A will end up having B's address in its ARP table and vice versa, but I am not sure about what happens with C.
Any help would be appreciated. Thanks in advance!