According to the Encyclopedia Britannica, personification is "a figure of speech in which human characteristics are attributed to an abstract quality, animal, or inanimate object." In the famous poem "Ode to the West Wind," Percy Bysshe Shelley personifies the west wind as a wild spirit with human-like qualities that functions as both a "destroyer and preserver."
Shelley first describes this wild spirit as an "enchanter" that drives multicolored autumn leaves before it. The autumn leaves have died and fallen off the trees, and so the poet likens them to "pestilence-stricken multitudes." A pestilence is a plague or serious illness that kills people, so this image is obviously of the wind as destroyer. In contrast, the poet then says that the wind at the same time also hides the "winged seeds" in their "dark wintry bed" until spring comes and the seeds sprout. This image shows the wind as preserver.
The poet describes how the wind sweeps the clouds along, bringing rain and lightning, and also how the wind creates a pattern in the clouds that looks like the hair "of some fierce Maenad." The Maenads were women who were devotees of Dionysus, the Greek god of wine. They would go into mad, ecstatic dances while they were worshipping. The poet suggests that the wild wind sculpts cloud patterns in the sky that suggest this wild abandon.
The poet says that the wild spirit of the wind is also a singer of dirges, which are songs sung at funerals. In this case, the wind sings the death of the old year as it descends into winter.
The late-season wild spirit of the west wind wakens the Mediterranean Sea, which sleeps during the summer, and causes the Atlantic Ocean to create chasms between tossing waves.
Finally, the poet calls upon the west wind, as if it were sentient, to become the wild spirit of inspiration for him. The poet wishes to be like a leaf or cloud or wave so that the wind can touch and move him. He wants to scatter his words among mankind and be as "the trumpet of a prophecy." However, like the wild spirit of the wind, the poet longs to be not destroyer only but also preserver, as evidenced by the last line when he states that the winter blowing of the west wind means that spring will eventually follow.