Final answer:
In 'Sonnet 18' by Shakespeare, the speaker states that his beloved's 'eternal summer', which refers to their beauty and essence, 'shall not fade' due to being immortalized in the sonnet.
Step-by-step explanation:
In Shakespeare's "Sonnet 18," the speaker asserts that his beloved's 'eternal summer shall not fade.' This metaphor suggests that the beauty and essence of the speaker's beloved will remain forever young and will not be lost to the ravages of time. The speaker immortalizes the beloved through the lines of the poem, suggesting that as long as people can read and appreciate the sonnet, the beloved's memory and beauty will persist.