In “Sonnet 18” Shakespeare speaks to the external nature of love. He explores his feelings for his love, concluding that she will both live eternally in these lines and grow more beautiful with each reading. The controlling metaphor of the sonnet is a summer’s day to which Shakespeare’s beloved is compared. This sonnet begins with the comparison to a summer’s day, elaborates on that metaphor throughout, and ends with Shakespeare’s reason for writing these lines. Shakespeare establishes the subject of this sonnet in the first line, which is also the metaphor that is strung throughout. He asks both himself and the reader, “Shall I compare thee to a summer’s day?” The second line, “Thou art more lovely and more temperate,” sets the mood for the sonnet, as it depicts Shakespeare’s view of his love. Lines three and four shift to the details of summer and how they compare to her. The summer’s day metaphor continues and develops in the second quatrain. Lines five and six include personification when Shakespeare writes “Sometimes too hot the eye of heaven shines.” These lines intensify the sonnet, because Heaven is a delicate idea that shares a connection with his feelings for his love. Lines seven and eight foreshadow the sonnet’s turn as they state that everything in nature seems to fade away at some point or another. The first two lines of the third quatrain contain the sonnet’s turning point, where Shakespeare states “But thy eternal summer shall not fade,” At this point, Shakespeare stops comparing details of a summer’s day to his love. Instead, he moves into why he decided to write these lines. In line eleven, Shakespeare uses personification again when he says “Nor shall death brag thou wand’rest in his shade.” Like lines five and six, death is a serious concept that correlates to Shakespeare’s feelings for his beloved. Additionally, line twelve captures Shakespeare’s use of metonymy in which “eternal lines,” that refer to the sonnet as a whole allow Shakespeare’s beloved’s beauty to grow with each reading. This sets us up for the sonnet’s conclusion. In lines thirteen and fourteen, Shakespeare claims “so long as men can breathe, or eyes can see, / So long lives this, and this gives life to thee.” In other words, he argues that as long as people live on this Earth, his love’s life and beauty will live forever in this sonnet. These last lines explain Shakespeare’s purpose for writing this sonnet, which is to give his beloved eternal life.