In his own words
Sonnet 18
Shall I compare thee to a summer’s day?Thou art more lovely and more temperate:Rough winds do shake the darling buds of May,And summer’s lease hath all too short a date:Sometime too hot the eye of heaven shines,And often is his gold complexion dimm’d,And every fair from fair sometime declines,By chance, or nature’s changing course untrimm’d:But thy eternal summer shall not fade,Nor lose possession of that fair thou ow’st,Nor shall death brag thou wander’st in his shade,When in eternal lines to time thou grow’st, So long as men can breathe, or eyes can see, So long lives this, and this gives life to thee.
The most famous opening question in English. The comparison fails on purpose: summer fades, and the poem is built to outlast it. The last two lines state the wager plainly, and so far they have won.