Final answer:
Shakespeare's line from Sonnet 18 metaphorically describes summer as having a lease with a short date, highlighting the temporary nature of its beauty in contrast to the beloved's eternal elegance preserved by the poem.
Step-by-step explanation:
The line "And summer's lease hath all too short a date:" from Shakespeare's Sonnet 18 reflects on the transience of summer, likening it to a short-term rental agreement that expires too soon. This showcases the ephemerality of summer's beauty, an essential theme throughout the sonnet. In contrast to summer's fleeting nature, the speaker suggests that the beloved's beauty is eternal, especially through the preservation of the poem. This comparison underlines the power of poetry to immortalize that which is otherwise temporal.