Method and system for expanding function of message in communication session

A system includes a memory configured to store computer-readable instructions; and one or more processors configured to execute the computer-readable instructions such that the one or more processors are configured to, receive a message from a first electronic device connected to a communication session for an instant messaging service, determine hidden attribute information for playing content corresponding to a keyword using the keyword further included in the message, if the message includes a desired character, add the determined hidden attribute information to the message, and transmit the message to which the hidden attribute information is added, to a second electronic device connected to the communication session through the communication session.