Not all metadata is delivered to all sites, and not all sites will make all of your release metadata public, but any site could choose to do so. This includes not only the title and artist, but also your songwriter and/or publisher names.
The industry overall is trending toward making this information more publicly visible and searchable, so please assume that any information you enter on your release might be visible to your listeners! Exercise caution with what info you include, and if there is anything you want to keep private, don't include it.