What ideas and feelings does lord capulet convey in the simile in lines 28-29?

In this line, Capulet says:

"Death lies on her like an untimely frost Upon the sweetest flower of all the field."

He is literally describing the sight of Juliet in death. He is comparing her to the sweetest flower caught in an early frost. Like the flower, Juliet has died too soon.

With these words, Capulet is conveying both the depth of his love and of his grief. He clearly loves his daughter and is completely devastated by her untimely death.