Krsna is known as Madana-mohana because He conquers the mind of Cupid. He is also known as Madana-mohana due to His bestowing favors upon the damsels of Vraja and accepting their devotional service. After conquering Cupid’s pride, the Lord engages in the rasa dance as the new Cupid. He is also known as Madana-mohana because of His ability to conquer the minds of women with His five arrows of form, taste, smell, sound and touch. The pearls of the necklace hanging on Krsna’s neck are as white as ducks, and the peacock feather decorating His head is colored like a rainbow. His yellow garment is like lightning in the sky, and Krsna Himself is like a newly arrived cloud. The gopis are like food grains in the field, and when the cloud pours rain on those grains, it appears that Krsna is nourishing the hearts of the gopis by calling down His pastime rain of mercy. Indeed, ducks fly in the sky during the rainy season, and rainbows can also be seen at that time. Krsna freely moves among His friends as a cowherd boy in Vrndavana, and when He plays His flute, all living creatures, mobile and immobile, are overwhelmed with ecstasy. They quiver, and tears flow from their eyes.

From Teachings of Lord Caitanya, by Srila Prabhupada, Ch. 10: The Beauty of Krsna