The primary function of the Greek god Hermes in mythology is that of a messenger and protector of travelers. He is often depicted with winged sandals and a caduceus, symbolizing his role in facilitating communication between gods and mortals. Hermes is also associated with trade, eloquence, and cunning, often acting as a guide for souls to the underworld. His multifaceted nature showcases the complexities of messaging and skill in ancient Greek culture.