Formal:
* Olá, meu amor. (Formal and polite)
Informal:
* Oi, meu amor. (More casual and affectionate)
* Oi, meu bem. (Similar to "my love" but slightly more informal)
* Oi, meu/minha [name]. (If you're using their name, this is a very common greeting)
More affectionate:
* Meu amor, oi. (More romantic and emphasizes the "love")
* Meu bem, oi. (Similar to above, but slightly less romantic)
Remember:
* Meu amor is a general term for "my love" and can be used for romantic partners, family members, or close friends.
* Meu bem is slightly more informal and can be used for romantic partners or close friends.
* You can also use just Oi or Olá followed by your partner's name.
The best way to say it depends on your relationship with the person and the tone you want to set.