I have attended live performances at the Met, but since I don't live in NYC I mostly attend the Live in HD performances at a local movie theatre. Taking the 1.5 hour backstage tour was a real treat - seeing the workings of the enormous stage, the costume workshop, a dressing room, and a peek into a rehearsal room where two famous stars were in rehearsal. The tour guide was enormously knowledgable.
There is a lot of walking on the trip, and quite a bit of standing. One elderly woman brought a portable stool, which seemed to work well.