Shall I compare thee to a summer’s day? Thou art more lovely and more temperate (1-2)
At first glance, the poem seems to start like a really awkward little love poem, doesn’t it? It feels like the poet is almost awkward in professing his love. He has to ask whether he ought to go ahead with the comparison (couldn’t he just make the comparison without all the anxiety?), and the best compliments he can come up with are "lovely" and "temperate." This isn’t high-flown language, and there’s nothing particularly inspiring here. If we didn’t have the rest of the poem to go on, we’d think this poem was by some sad sap who had no idea how to express himself poetically. Instead, though, once we get to the end of the poem, we realize that these lines sound awkward because the speaker’s heart isn’t really in it. He’s into himself and the idea of writing a poem, and it’s only there where his language can shine.
But thy eternal summer shall not fade (9)
In line 9 we come to realize that this whole comparison with the summer is bizarre. Check out this line: "thy eternal summer shall not fade." That’s like saying "thy unbreakable armor shall not be broken." Duh, his/her eternal summer won’t fade, because it’s eternal. Plus, there’s the added issue that the comparison of real summer to the beloved’s "summer" doesn’t fully make sense. The speaker is claiming that the real summer is temporary, while the beloved’s metaphorical summer is eternal. But the problem is, even the real summer is eternal, because it happens every year. The line "summer’s lease hath all too short a date" doesn’t entirely make sense, because even if each individual summer is limited, summer itself is eternal. To us, all of this just helps torpedo the thought that this is a legitimate love poem for anyone other than the poet.
Nor shall death brag thou wander’st in his shade, When in eternal lines to time thou grow’st (11-12)
In the thoughts accompanying lines 1-2 above, we mentioned how the "love poem" feels a bit hollow and falls flat in the first two lines, as the poet just doesn’t seem to be able to turn his love into beautiful language. Well, we see in lines 11-12 that he is fully capable of turning his love into beautiful, richly imagistic language. The thing is, he reveals his true love here: himself, or the guy who can fend off death.