Exiftool is by far the best and most extensive metadata tool available!
It reads and writes metadata information from/to many files, but primarily focuses on photos/images. It reads/writes EXIF, GPS, XMP, maker notes for many cameras, JFIF, GeoTIFF, ICC Profile, Photoshop IRB, FlashPix, VRA Core 4, ISAD(G) and many, many more tags.
It can use a “reference” image to write the tags to a multiple set of photos or a complete directory containing photos.