Romeo glorifies Juliet's beauty by comparing her appearance to objects and abstract concepts observable in nature. In his soliloquy in act 1, scene 5, Romeo compares Juliet to fire light, a star or a planet in the night sky, and a dove in a flock of crows.
By elevating Juliet's beauty to the light of a fire, Romeo is suggesting that her beauty has significant power. Fire is an element, one that has the potential to sustain life with its warmth and to take life away in its most extreme form.
By comparing Juliet to a "jewel in an Ethiope's ear," a metaphor for a planet or star, Romeo makes the grand claim that her beauty is otherworldly and exotic in its rarity. His amazement at her beauty is communicated in this comparison.
By describing Juliet as a dove amongst crows, Romeo expresses appreciation of Juliet's youth, glorifying her obvious innocence. A dove is white, while crows are black, and the color white is a symbol of purity.