Before 10 a.m. on a recent steamy morning, lines started forming up the front steps of the Metropolitan Museum of Art, with visitors clutching New York City street maps waiting patiently for the doors to open.

While the museum has always been a magnet for tourists during the summer months, New Yorkers who frequent the Met should be aware that there are many new things to see in its permanent galleries. Keith Christiansen, chairman of the museum’s European paintings department, has shaken things up a bit, hanging works lent for the summer and uniting treasures that have recently returned home after traveling to exhibitions around the world.