One archetype of the myth is the task.  The task of retrieving the Golden Fleece is one that no one would even dare.  The retrieval of the Golden Fleece was cast as "an impossible task."  Jason understood this to be the case.  He understands that this task is to be done by the bravest and most austere of warriors, of which Jason believes he embodies. Another archetype is the woman as seductress.  The women of the island of Lemnos are shown to be seductive forces, embodying the archetype of women as seduction, capable of diverting even the supposedly most focused of men.  

Along these lines, the archetype of the unfaithful woman is seen in Medea.  While traditionally unfaithfulness is seen as something in wives or girlfriends in literature, it is seen in how Medea is unfaithful to her father in order to have Jason.  She recognizes that if she helps Jason, he will remain with her. Medea is unfaithful to her family, and in particular, her father, in order to achieve what she covets.  Later on, she will prove to be unfaithful to Jason in the worst of ways.  Finally, the archetype of the evil and sinister serpent is seen in the force that guards the fleece. The serpent who never sleeps in the grove and is watching over the fleece is a reminder of the archetype that is such an embedded part of Western literature.