Formal:
* Je te garde à jamais. (I keep you forever.) This is the most literal translation, and it conveys the idea of keeping someone close.
* Je t'aimerai pour toujours. (I will love you forever.) This emphasizes the depth and permanence of your love.
* Tu es à moi pour toujours. (You are mine forever.) This emphasizes possessiveness and the feeling of being inseparable.
Informal:
* Je t'aime pour toujours et à jamais. (I love you forever and always.) This is a common and heartfelt expression.
* Tu es mon/ma tout pour toujours. (You are my everything forever.) This emphasizes the profound importance of the person in your life.
* Je serai toujours là pour toi. (I will always be there for you.) This focuses on your commitment and unwavering support.
Poetic:
* Tu es mon soleil, mon étoile, mon amour éternel. (You are my sun, my star, my eternal love.) This uses imagery to express your deep and enduring love.
* Notre amour est un lien indissoluble, pour l'éternité. (Our love is an unbreakable bond, for eternity.) This emphasizes the strength and enduring nature of your love.
It's important to choose the expression that best fits the context and your relationship with the person.