All of our digital images have metadata attached. At a minimum the camera will record the camera settings such as exposure, date, time, white balance etc. Cameras equipped with GPS receivers can also record the latitude and longitude of the camera when the photo was taken. Additional metadata including the name of the photographer, copyright info and keywords can be added to a file later using Photoshop, Lightroom and other software.
Metadata is useful. If your photo is in the public domain without metadata then it is essential up for grabs for anyone who wants to grab it.
Technically, your photo is copyrighted as soon as you take it but if no one knows it is yours then it’s considered and orphaned work. Here is a definition from Wikipedia:
“An orphan work is a copyright protected work for which rightsholders are positively indeterminate or uncontactable. Sometimes the names of the originators or rightsholders are known, yet it is impossible to contact them because additional details cannot be found.” ( https://en.wikipedia.org/wiki/Orphan_work)
Adding metadata to your photos can be done as part of your processing and is worth the effort, not just for copyright purposes but also for help find photos years after you’ve taken them just by using search terms for the keywords you added.
Another great reason is to get credit for your work when it appears on Google. Your metadata can now be found when viewers find your photos using Google Image Search. Here is a great article by IPTC News that is worth reading:
(https://iptc.org/news/google-images-now-displays-image-credits-based-on-iptc-photo-metadata/ )