what is the purpose of the appearance and speech of the messenger in scene 2 ? who might have sent this messenger?

Question

act 4 of macbeth 

Answer 1

The captain, who was wounded helping Duncan’s son Malcolm escape capture by the Irish, replies that the Scottish generals Macbeth and Banquo fought with great courage and violence. The captain then describes for Duncan how Macbeth slew the traitorous Macdonwald.