Answer:
Shakespeare uses Sonnet 18 to praise his beloved's beauty and describe all the ways in which their beauty is preferable to a summer day. The stability of love and its power to immortalize someone is the overarching theme of this poem.
Explanation:
The major themes of Shakespeare's sonnet
The sonnets cover such themes as the passage of time, love, infidelity, jealousy, beauty and mortality. The first 126 are addressed to a young man; the last 28 are either addressed to, or refer to a woman. (Sonnets 138 and 144 had previously been published in the 1599 miscellany The Passionate Pilgrim).
