“Lycidas” is an example of pastoral poetry, a genre that uses nostalgic scenes from the shepherd’s life to address universal themes. The Greek poet Theocritus popularized the genre with his Idylls, a series of poems structured around singing competitions between shepherds. At the time Theocritus was writing, Greeks already felt they had lost the simplicity of the rural life and looked back wistfully at the time when shepherds had roamed the fields tending to their flocks. At the moment of its invention, pastoral poetry already felt antiquated.
The genre is always looking back, and in this sense it’s appropriate for Milton’s depiction of a speaker who can’t stop grieving. By turning himself and King into two shepherds, Milton suggests their relationship is already part of the unrecoverable past.
Though Milton chooses to eulogize King through the pastoral, he also remains skeptical of the genre. The songs of the shepherds in pastoral poetry are performative, not genuine expressions of grief, and his speaker seems to sense that these tools will not succeed in communicating his emotion. By choosing a form he knows cannot express genuine feeling, Milton sets up his speaker to fail. He creates circumstances in which his poem cannot communicate the loss of King and poetry feels like an impossible way to mourn.