Usage patterns
〜の虜になるto become captivated by ~; to fall completely under the spell of ~
She became completely captivated by that music.
〈人〉を虜にするto captivate someone; to steal someone's heart
That smile captivated many people.
〈相手〉の虜になるto become a prisoner/captive of an enemy or opposing force
The soldiers became prisoners of the enemy.