Yeats' "Leda and the Swan" retells the legend of Zeus, who has fallen in love with Leda, descends upon her in the form of a swan and impregnates her with the child who will one day become Helen of Troy. This poem, published during Yeats' late period in 1928, is characterized by violence and reflects a comment Yeats made about his later poetry that they were infused with "lust and rage." Clearly, the violence with which the swan takes Leda is full of both.
The answer to the question as to whether Leda enjoys the encounter is difficult because, if we take the poem at face value, Leda is a victim of rape:
A sudden blow. . . .Above the staggering girl. . . .He holds her helpless breast against his breast. . . .How can those terrified vague fingers push. . . .
This attack--and it can be characterized as nothing but an attack--is violent in the extreme for two reasons: Leda is raped but her rapist is something that she would not recognize as being capable of such an assault. The rape, then, is doubly horrific because it violates not only Leda's body but her perception of reality.
But ambiguity exists in Yeats' description of Leda's reaction to the rape:
How can those terrified vague fingers push/The feathered glory from her loosening thighs?
First, "vague fingers" is a very odd phrase to describe a young woman's attempt to fend off a sexual attack, and we have to wonder if the vagueness is meant to describe a half-hearted attempt by Leda to stop the Swan's attack. At the same time, the use of "terrified vague fingers" implies that Leda may simply be so shocked that her actions are tentative. Second, her failure to keep the swan from "her loosening thighs" may imply, if not willingness, Leda's acquiescence in the rape--in other words, why are her thighs "loosening"? A reasonable interpretation of those lines is that Leda wilfully stops protecting herself, indicating a willingness to allow the rape.
This poem, for the reasons we've discussed above, has caused many critics to disagree on the question of Leda's reaction to the rape, and it is perhaps reasonable to conclude that, rather than enjoying the rape, Leda most likely allows the rape to continue because she realizes she is in the grip of an irresistible force and chooses not to fight.