What metaphors are used in The Love Song of J. Alfred Prufrock by T. S. Eliot?

The near repetition in lines 21 and 22 signals that Prufrock's attention has returned from the imagined room to his actual surroundings. It is evening, foggy, and his attention focuses on the fog mixed with chimney smoke, and then takes off in a metaphorical process that equates the movement of the fog with the movement of some seemingly cat-like creature around the structure of the city at evening. Prufrock's lyrical musing here reflects the dream-like emotional state evoked by the fog.