Well, first, the image will be shown, the black and white levels will be set, the white balance will be adjusted and a tone curve will be applied. With 16 bits to play, most of this can be adjusted later without much trouble, but is with losses The demonstration is irreversible. None of this is metadata, but it is important to know.
Second, there is information stored in something called "manufacturer's notes". This often contains elements such as the selected focus point, face detection information and other non-standard metadata. Sometimes this is even encrypted. Some programs will ignore this completely and, therefore, will not copy it to their new file.