Explanation: a metaphor is a figure of speech that consists in making a direct comparison between elements that aren't obviously related, in order to create an image in the reader's mind. In the given lines from Sir Philip Sidney's sonnet, we can see an example of a metaphor, that compares Stella's eyes to bright beams. It isn't a simile because it doesn't use the words "like" or "as" to make the comparison, it doesn't use similar grammatical structures, so it isn't parallelism, and it isn't a hyperbole because it isn't exaggerating.
"Bright beams" that Nature has wrapped in black are Stella's eyes. In a way, it is also a simile, but every metaphor is a contracted simile (without "like").
There are other literary devices in this passage as well: contrast (black - bright), rhetorical question (one that doesn't have an answer, or an answer is obvious)...
