After you know the basics for an instrument and you can play a few songs, it becomes more and more attractive to play freely any song you hear and like. This is not that difficult ones you know the chord progression for a song. Hooktheory is a huge database for chord progressions but, in contrast to other websites, it gives you the relative chords for a certain key (like VI-IV-I-V) and not the name of the chords in a certain key (like Am-F-C-G). This is exactly the way a musician needs it when you have your favorite keys in which you like to play and you are just interested in the progression itself. It is also a much better way to understand the principles behind music. Hooktheory is a great website for this as the database has a very high quality standard, provides the chords along with a midi-file and a Youtube-video of your song and displays the chord progression for any key you like.

And to get an additional boost of motivation to learn how to play any song you like, I recommend all the videos created by Collective Cadenza.