You can use the metadata write functionality to change existing metadata of files. Select Metadata in the menu and you
will see the window below. Choose the tag to change and fill in the value of "New value". When finished click "Start batch".
If all files should have the same value, you can click the action button and click "Copy value to all".
You can only change metadata fields, like Exif metadata, that already have values. You cannot add new fields. It is recommended to
backup all the files prior to running a metadata write batch.
Also note, this will only work on some file formats. Will not work with ID3 tags in MP3 files.