In the poem ‘Daffodils’ or ‘I wandered lonely as a cloud’ the poet has used several figures of speech to give it a rhetorical effect. Those are elaborated below.

Simile
Simile is a direct comparison between two different things using ‘as’ or ‘like’.

I wandered lonely as a cloud

In the above line, the poet has compared himself to a cloud using ‘as’. This is an example of simile.

Continuous as the stars that shine
…margin of a bay

In the above extract the poet has compared the flowers with the shining stars on the Milky Way.

Alliteration
Alliteration is the repetition of consonant sound at the beginning or in stressed syllables of nearby words.

Beside the lake, beneath the trees,

And dances with the daffodils

The repetition of the sounds ‘b’ and ‘d’ in above lines are examples of alliteration.

Hyperbole
Hyperbole is an exaggerated statement.

When all at once I saw a crowd,

Ten thousand saw I at a glance,

In the two examples above, the poet has used ‘crowd’ and ‘ten thousand’ to mean a lot of daffodils. But he must not have counted them there at a glance. This is an obvious exaggeration.

They stretched in never-ending line

Yes, the flowers were stretched in a vast area, but that is surely not ‘never-ending’. The poet has made an overstatement here.

Personification
The poet has attributed human characteristics to the daffodils (non-human objects) in this poem.

Fluttering and dancing in the breeze

Tossing their heads in sprightly dance

Out-did the sparkling waves in glee

All the above lines are personification of the flowers.

The waves beside them danced;

Wordsworth has personified the waves in this line.