"Sonnet 18," written by William Shakespeare, is one of his most famous poems. It begins with the speaker comparing a beloved person to a summer's day, suggesting that the beloved is more beautiful and temperate. The poem explores themes of beauty, nature, and the passage of time. Throughout the sonnet, the speaker argues that while summer can be fleeting and imperfect, the beauty of the beloved will endure through the poem itself. By immortalizing the beloved's beauty in verse, Shakespeare asserts that art can transcend time and preserve what is beautiful forever.