Is the parking garage underneath the Met open on the days the Museum is open? If so, what is the cost? Do we need to reserve a spot? Is the best entrance off 5th Ave. & 87/86th Street?

The Bestparking app shows the cost to be about $50 for a typical 6-hr weekday. You can find less expensive parking from Bestparking or Spothero apps.

https://nycparkingauthority.com/metropolitan-museum-art-parking-guide/ The Museum parking garage, located at Fifth Avenue and 80th Street, is open 24 hours a day, seven days a week. For rates/costs refer to for all hours and member prices: https://www.metmuseum.org/visit/directions-parking