Figurative language is meant to create a picture in the reader's mind as well as feeling the emotions of the pictures. Lines one and two compare a person to a summer's day which is a metaphor comparing two unlike things without using like or as because she is more lovely.   If you look at "too hot the eye of heaven shines", this could be a personification making the hot sun an eye which is a human characteristic  and a participant in the comparison of his beloved to a summer's day. The sun is also given a "gold complexion"  which is personification as only people have a complexion.  "Nor shall death brag" is personification as only people brag, not death.  The emotional effect is that the author will not let death take over his beloved which shows the depth of his emotion.  He even states that this poem or sonnet will give life to his beloved forever as the poem will live and that is what will keep the memory of his beloved alive.