In the first quatrain the lyrical I asks a rhetorical question to the fair youth. He asks him if he can compares him to a summer’s day. The speaking voice says that the fair youth is more lovely and more temperate than a summer’s day. He says a summer’s day is too short compared to the love for the fair youth.

In the second quatrain the speaking voice underlines the defects of a summer’s day: it is messy and too hot and his beauty declines.

In the third quatrain, the lyrical I says the fair youth’s eternal summer will not fade, he will not lose his fair because he will live in that eternal lines.

In the rhyming couplets the speaking voice says that so long as men will live, so long live this lines and consequently the fair youth.

From the syntactic point of view, the “eye of heaven” in line 5 stand for the sun. In the second stanza lines 6 and 7 begin with the same word “and” to reinforce the meaning of this lines; the same happens in the third stanza in lines 11 and 12 with the word “nor” and in the rhyming couplets with the words “so long”.