It seems like every time you figure out the Music app on your iOS device Apple redesigns it. In the latest revamp, iOS 10.0 or later, the repeat song function can be found in the Now Playing screen under the music and volume controls.
Here's how to set a song to repeat in the redesigned Music app:
- Open the Music app and tap the current song panel at the bottom of your display.
- Swipe up on your display until you see the Shuffle and Repeat buttons.
- Tap Repeat and the selected song will repeat itself until you stop it.