Lyrics for any iOS music?
Any app that plays songs from the device library can read song title, artist, album and a lot more, this is included in the Apple Framework.
Lyrics can be read as well, so long as they are included in the meta data of the song file. Most songs don't include this information, so the lyrics meta data is empty.
If you subscribe to Apple Music, it will load lyrics for songs you have purchased.  An app called Get Lyrical can also look up and install lyrics.  Finally, you can type or paste them yourself in the Get Info window.
The only other way to get the lyrics is to load a separate file such as an .lrc  This is why apps that show lyrics require you to play the song in them, because they have written some code to display .lrc file contents, or the meta data if available. .lrc files can also contain time data so can sync the playback to the lyrics, meta data does not normally do this.