Pack small gaps firmly. Secure the filling so mice cannot readily dislodge it.
Use compatible sealant to retain the metal and close remaining gaps. Follow the sealant instructions.
Damp spots and outdoor exposure need inspection. Replace deteriorating repairs and fix moisture problems.
Copper exclusion mesh does not rust like ordinary steel wool. It still needs firm packing and secure retention.
Use securely fixed hardware cloth or metal flashing when a soft metal plug lacks support.
Use a suitable vent guard. Never stuff metal filling into dryer exhausts, drains or required air openings.
Compare materials, wear gloves and check every edge after the repair cures.