actualmermaid:

There is a sexual aspect to her relationships with those she chooses to instruct in the art of enchantment—Melian gladly shares her secret knowledge, but rarely, and only with women. Sex with Melian goes much further than physical pleasure, expanding her partners’ minds to rhythms and powers beyond the physical sphere, which are necessary to understand Melian’s secret arts.

Also, it’s fun for everyone involved. Melian is the toppiest top who ever topped, and she would be the absolute most annoying kind of philosophical bondage enthusiast if she didn’t have eternal, supernatural experience and perspective. She is always loving and attentive and eager to share what knowledge she can with her partners, who, while immortal, are not eternally tied to the music of the universe in the same way that she is. Everything she does reflects her love for the children of Ilúvatar and her eagerness to show them a fraction of what she sees.

Thingol, on the other hand, is special. Melian’s relationship with her protégés is about opening a window for them into her perception as a Maia, but with Thingol, she learns about inhabiting a body, being a partner and a mother, and experiencing flesh like one of the elves.