With an Apple Watch running watchOS 4.1 or higher, you can listen to music on your watch, including songs, albums, playlists, and Apple Radio stations from Apple Music (if you're a subscriber), as well as apps such as Spotify, Pandora, and iHeartRadio.
To set this up, first connect your earbuds, headphones, or speaker via Bluetooth. Open Apple's Music app on the watch to swipe through your library of music. From the player, you can pause, resume, skip ahead, go back, and control the volume. With the built-in radio feature, you can tune into Apple Music 1 and certain news and music stations.
Third-party music apps will need top be downloaded through the App Store on your watch. Each app is slightly different, but the process is similar—just fire up the app to access your stations or library. Some watch apps even allow paid subscribers to listen to music offline.