The Happy Prince is like a fairy tale but more appropriately it is an allegory bringing out the importance of love, sacrifice and charity.
The first theme is that outward appearance is not the yardstick of measuring beauty. The Prince who is laid bare with a broken heart in the priced possession of God and not when he is decorated with Gold and precious stones. The prince has a lead heart but it is full of sympathy.
The second theme is that love and sacrifice are two saving forces. The world is full of hypocrisy and exploitation but the sacrifice and charity of the Prince and the swallow stand out.
The third theme is the wide gap between the rich and the poor. The author wanted to bring out the Victorian society which had a similar chasm between the rich and the poor where the poor had to undergo exploitation due to the industrial squalor.