A man who is husband material can see a standard woman and think she’s the greatest thing ever. This man will make a great husband. Even though the lady is pretty standard, the husband treats her like she’s anything but.
It’s pretty standard for a husband and wife to exchange vows when getting married, and the husband said this girl held the key (き) to his heart. She unlocked the husband’s heart with the key and now he’s a man made whole.