We can help you get started on this. The poem is about the season, autumn, so to find metaphors and other figures of speech, look at each line to find how the poet describes the season. What do you think about when you think of autumn? Leaves changing colors, a crisp coolness to the air, approaching holiday season? Keats writes about the images he associates with autumn in the same way:
SEASON of mists and mellow fruitfulness,
Close bosom-friend of the maturing sun
In autumn, the air is "misty" and the fruits are ripe. This is a metaphor. In the second line, there is personification, stating that the season of autumn is a "friend" to the sun. The image here is that the sun is high in the sky, causing the fruit to ripen, so the sun and autumn are "friends" working together to ripen the fruit. These images are continued in the following lines. Can you find some other figures of speech in them in this first stanza?
Look at the second stanza. There is quite a bit of personification in this stanza. Doesn't it seem as if the poet is talking about a person? But no, it is still the season he is describing.
Who hath not seen thee oft amid thy store?
Sometimes whoever seeks abroad may find
Thee sitting careless on a granary floor,
Thy hair soft-lifted by the winnowing wind;
If you go through the poem in this way, you will find other figures of speech, such as similes:
And sometimes like a gleaner thou dost keep