Expressing strong affection:
* Head over heels: This describes someone deeply in love or infatuated.
* Smitten: Implies a sudden and intense feeling of attraction.
* Taken with: Expresses being captivated by someone or something.
* Blinded by love: This suggests someone is so enamored they can't see clearly.
Expressing admiration or fascination:
* Mesmerized: Being completely captivated or enthralled.
* Spellbound: Completely captivated by someone or something.
The best idiom to use will depend on the specific context and the intensity of the feeling you want to convey.