The themes include transformation. In the story of Apollo and Daphne, Daphne was transformed into a laurel tree to avoid Apollo's love. Unrequited love is also a theme. Pygmalion loved his statue which couldn't initially love him back. And then there's the theme of divine intervention. In the case of Pygmalion, Aphrodite brought the statue to life. In the story of Baucis and Philemon, the kindness of the couple was rewarded by the gods, showing the theme of divine justice in relation to love.
One main theme is the power of love over obstacles. For example, in the story of Eros and Psyche, Psyche had to face numerous challenges because of Aphrodite's jealousy, but her love for Eros helped her persevere. Another theme is the idea of forbidden love, like Paris and Helen. Their love led to war as it was considered a wrong act to take another man's wife. Also, sacrifice is a theme, as seen in Orpheus and Eurydice. Orpheus risked his life to go to the underworld to get Eurydice back.