It's a feature most music streaming services have, so it's good to know that YouTube Music is following suit. The mobile app of the service now adds song lyrics to individual song pages, letting you have that impromptu karaoke session of your dreams. But you're going to have to do your scrolling. The feature doesn't automatically scroll in time with the song. If you want to pull up the lyrics, you need to play a song first, then tap on the small "i" icon on the bottom left side of the screen. The words will show up similar to how they are presented in Google Search.
Source: SlashGear