Michael D Sullivan wrote:
dj_paiges's answer is not wholly correct. You can add a text layer to a photograph and then add text over the photo or in the margin (enlarge the canvas size if necessary), and then flatten the image and resave as a jpeg or png image file. This will superimpose an image of the text over the picture, but will not produce searchable text words like the metadata option will.
There are no layers in Lightroom. This is impossible in Lightroom