Keats often looked to nature for poetic inspiration. These first lines of this poem illustrate his fascination with natural imagery and how it inspires and energizes his poetic mind. In the first line, he is standing on a hill on his toes so that he can look at the landscape from the highest point possible. Nature was a calming, meditative, and transcendent place for Keats. In the second line, the still air suggests a calm atmosphere. The buds are "modest" because they almost appear shy, still in the process of opening. They droop away from the plant and since they are still opening, they have the crown (diadem) shape. They still have dew on them ("sobbing of the morn") and therefore, it must be close to morning. This image of buds opening, still with dew, early in the morning, creates images of freshness, newness, and purity. 

The clouds are as white as freshly shorn sheep. They "sleep" and/or drift gracefully in the sky ("blue fields of heaven"). The "noiseless noise" is the wind drifting through the leaves. The wind is noiseless on its own; it needs the leaves to rustle in order to make noise. The wind is born of (comes from) the sky (heaven). These associations with heaven give a spiritual notion to these movements, sights, and sounds in nature. Later in the poem, Keats will invoke mythological characters, continuing with this conflation of the natural with the spiritual. Although he hears the wind through the trees, the leaves move imperceptibly. He hears the "noiseless noise" but can not see the "faintest motion" that causes the sound.