Apple Music/iTunes is respected as the industry standard when it comes to formatting metadata. They have been enforcing their style guide since the launch of iTunes, and keep it updated every year.
iTunes Store Music Style Guide
While this document is very long, and exhaustive, we've highlighted a few common errors that we see every day. Apple will remove your music from the store until errors are fixed, so it is best practice to ensure you are submitting metadata to their guidelines to prevent your content from being proactively removed by Apple.
Do not list your artist name in the song, or release title.
Similarly, do not list your artist name as a featured artist (you are already listed as a primary, and primary artists cannot be listed as a featured artist).
Do not list your producers in the track or release title.
Do not list in the track title that the track is "Clean" or "Explicit"
Do not include any website or social media links on the cover art.
Do not include any images, or persons within your cover art that you do not have the rights to use. That is especially true for other artists, athletes, or logos for prominent brands.
If you are listing multiple featured artists, please separate them in separate listings. Do not list them as such; "Artist 1 x Artist x Artist 3", or "Artist 1,Artist2,Artist 3" or "Artist 1 & Artist 2 & Artist 3".
If you have specific questions about iTunes metadata guide, please reach out to us at email@example.com and reference the area in question. We are happy to help out!