Hello abbassms77,
If the Music app will not load, first confirm that your internet connection is working. Go into an app like Safari and confirm that it is able to load. If the device is connected to a Wi-Fi network, also try using the cellular connection instead to rule out a network issue.
If the issue is isolated to the Music app, try completely quitting and reopening it.
1. From the Home Screen, swipe up from the bottom of the screen and pause in the middle of the screen.
2. Swipe right or left to find the app that you want to close.
3. Swipe up on the app's preview to close the app.
Close an app on your iPhone or iPod touch
You'll also want to make sure you've covered the basics like restarting the device and making sure it's up to date.
Restart your iPhone
Update your iPhone
If the Apple Music service is still not loading, you'll want to contact Apple for assistance: Get Support
Cheers!