The primary role of Hermes in Greek mythology is as the messenger of the gods. Hermes is known for his speed and cunning, facilitating communication between the divine and mortal realms. He also serves as the god of trade, thieves, and travelers, embodying aspects of commerce, skill, and transition. Hermes plays a crucial role in guiding souls to the afterlife, emphasizing his versatility and importance in both the human and divine order.