Something that surprised me about this poem is the fact of how we are expected to know the storyline behind the lines.  Yeats is expecting for his reader to know the myth of Helen of Troy.  Also the fact that this act of rape is supposed to be seen as something quite erotic, but as a reader today, I saw a different side to it.  Being raped is something that impacts one life greatly, but in this poem we almost see it as a norm.  Not normal in the sense that it is just ok for the “swan” to rape someone, but normal in the aspect of the mood you are supposed to get from it.  As if she was almost willing to be raped.  The poem is a sonnet in which we see a volta in about the tenth line, “A shudder in the loins engenders there.” This “swan” or “Zeus” then impregnates Leda, which is supposed to be a beautiful thing.  Yeats uses a rhyme scheme of ABAB CDCD EFG EFH.  There is an aggressiveness to the poem in which the girl seems to have no control.