My literal favorite trope/character interaction ever is when the monster is 101% head over tail/claws/fins/hooves in love with the human, including actions such as, but not limited to:
-dreamy sighs when they think about the human, and they think about them often.
-smooshing their face into the human while nuzzling them, then trying to play it off like nothing special.
-cradling their face in their hands as they make goo-goo eyes when they think no one is looking at them.
-getting overly hype about any casual physical contact whatsoever.
-talking at length about their extra special human to their monster friends/family.
-bringing the human rare or difficult to obtain objects because they can and plus wHAT IF THE HUMAN SMILES AND HUGS THEM AS A THANK YOU. IMAGINE.
-defending the human from less friendly monsters.
-STARTING OFF AS A NON-FRIENDLY MONSTER, AND FALLING IN LOVE WITH THE HUMAN ANYWAYS!!!!
If anyone wants to add their own, I would love to read them! I am always here for monster/human romance!!