Step 1: Understanding the Concept:
This question asks about a specific metaphor used in the poem 'Koel' by Puran Singh to describe the bird's song.
Step 2: Detailed Explanation:
The poet is struck by the intense, passionate, and almost painful sound of the Koel's cry. He uses powerful, burning imagery to describe its effect.
He feels that the song is so potent that it sets the leaves and the listener's soul ablaze. The poem contains the line where the poet addresses the bird, saying, "thy notes are a rain of fire." This metaphor powerfully conveys the burning intensity and passion the poet perceives in the bird's song.
Step 3: Final Answer:
The Koel's songs are compared to a rain of fire.