Metaphors in My mistress eyes'

Oh how I hate Shakespeare. But, this is the first work of his that I've read that wasn't a play and its not too bad. Characteristic of his plays, he uses a sort of dry humor in this poem. He describes his mistress as everything but ideal in saying metaphors like "My mistress' eyes are nothing like the sun" and "I have seen roses dmasked, red and white,/ But no such roses see I in her cheeks." All of these are a play off the typcial love poems that talk compare a woman to the beauty of nature, like the sun and roses. His metaphor serve a purpose in that they aren't lofty and idealistic, but more realistic. He still calls her great and "rare" in the last line, but he isn't over-the-top with her beauty and his infatuation of her. This is more of a love poem than any I've heard in that he points out the flaws and still accepts her as rare that no other woman compares to.