Describe the images, figures and rhyme scheme of "Sonnet 18".
There's an extensive, line-by-lne discussion of William Shakespeare's sonnet 18 at the web site given below.
To answer your question quickly, though, let me say that following:
The rhyme scheme is pretty much what is expected of a Shakespearean sonnet: ABAB CDCD EFEF GG
Each letter in the rhyme scheme represents a syllable sound, so the stanza with the ABAB rhyme scheme has the first and third lines rhyming ("day" and "May") and the second and fourth lines rhyming ("temperate" and "date"). You will notice that this pair of rhymes is a little forced or perhaps less pure than it was in Shakespeare's time: modern speakers tend not to stress the "ate" in "temperate" but do stress the monosyllabic word "date," making the two not really rhyme all that well.
The imagery would be, put simply, all of the descriptive word-pictures surrounding a beautiful summer day that are mentioned in the poem, particularly the extensive descriptions of the sun.
There are probably a number of figures of speech. I'll name only one: personification. The sun in the poem is said to have an "eye" and a "complexion" and is refered to as male ("his"). Attributing human features to an inanimate object is personification.
This poem has been discussed a great deal on this website. Maybe you can use the search feature to find those discussions.