Aeralfos are the small flying dragons with shields in the City In The Sky. Whenever they fly in the air, wait for them to put their shield up and flap their wings rapidly. Z target their shield and use the Clawshot to pull it toward you, then slash at it with your sword as much as you can. Just make sure not to use the Clawshot while the Aeralfo is on the ground or else it will pull you toward it and slash you.
If you’re having a hard time shooting your Clawshot at the right moment, shoot the Aeralfo with an arrow. It will then raise its shield to block your arrow, giving you a chance to use your Clawshot and pulling him down. Start attacking him until he starts blocking again. Repeat once he flies back into the air. When fighting the mini-boss versions, they will fly out of the windows on the walls. Be sure to pay attention to which window he enters. Block with your shield if he dives at you.