In this poem the speaker sees in the force and majesty of the West Wind a power that is to be admired and a power that is capable of bringing massive change. He therefore finds an apt link between the way that the wind ushers in new weather conditions and what he desires to do with his poetry, which is to foment revolutionary thought.
In the first section, the poet asks the west wind to listen to him. He sees the west wind as both a destroyer and preserver of aspects of autumn, and he looks forward to the springtime as a time when life is renewed. In this section, he focuses mainly on the effects of the wind on the land.
In the second section he focuses mainly on the effects of the wind on the ocean. Once again he emphasizes the enormous power of the wind.
In section three the emphasis on the effects of the wind on the sea continues. Here, though, the imagery is much less threatening than the imagery in the second section, except in the final two lines.
In section four the poet imagines what might happen if he were moved by as mighty a source of inspiration as the wind. He regrets that he has lost the vitality he enjoyed when he was young.
In stanza five he calls upon the wind to inspire him and revive him so that he can spread his prophetic ideas far and wide; in the final lines he looks forward to the arrival of spring and symbolic renewal.
The poem is about a poet's desire to help others, and to be the voice of revolution. Basically, Shelley believed that poets had a role in revolution, and a poet's voice should be inspirational and a revolution needs a poet's support to help the people be inspired.