Genius lyrics are now available in Apple Music. Genius is a music encyclopedia and lyrics database, and has recently partnered with Apple Music. Furthermore, Apple Music is now the official music player for Genius, as a web-based player (via The Verge).
Genius lyrics can be found on the Apple Music web player on the Genius website, as well as the Apple Music app.
Apple Music users can read Genius lyrics and annotations while they listen to a song.