What can the west wind do to the clouds in "Ode to the West Wind"? What are clouds compared to?

In Section 2 of Percy Bysshe Shelley's "Ode to the West Wind," the poet continues his description of the powerful West Wind by describing its effect on the clouds. The wind bears along the clouds as a stream bears along leaves that fall into it. Although line 15 implies the action of the wind by comparing it to a stream that carries fallen leaves, the more explicit description of the wind's action on the clouds occurs in line 44: "If I were a swift cloud to fly with thee." From these two lines, it is clear that the wind has power to move the clouds in the direction it is moving; it causes the clouds to fly along with it.
Section 2 compares clouds to leaves and angels. First, Shelley states that "loose clouds like Earth's decaying leaves are shed," comparing clouds to leaves that fall to the earth in autumn. Taking the analogy further, he says that the branches from which the clouds fall are the "tangled boughs of Heaven and Ocean."
In the second stanza of Section 2, Shelley writes that the clouds are "angels of rain and snow." Although he uses the term "angels" in its sense of "messengers," using that word also makes an implied comparison between clouds and angelic beings.
After comparing the wind to a stream and the clouds as objects that flow or fly along with it, Shelley states his wish that his words could travel over the universe in the same unimpeded way.