When I edit a raw photo in Photoshop from Lightroom, this picture loses its metadata? How can I keep the metadata created in Lightroom after editing in Photoshop?
Are you creating a new document by using “Save As” when you finish editing in Photoshop?
To my knowledge when you send an image to PS from LR using the "Edit In" option/feature PS does not strip any Metadata from the image. Even if you use the Save As option in PS to save it to some other format than the one you have chosen in the External Editor section of the LR preferences.
If you first Export the image, using the Export feature in LR before Opening the image in PS, there is an option in the Export dialog to included only certain Metadata in the image. Like just the Copyright or other such options.
The question is what makes you think the metadata is being removed?