Now you know the rhythm part for this song, let's take a look at the lead guitar. There is also a Jamzone article for this ActionTab.
The song is in the key of Bb Major. This means that the Bb Major scale is the central scale for the song - all the chords and melody lines will (more or less) fit with the Bb Major scale:
Bb - C - D - Eb - F - G - A - Bb
The lead guitar uses notes from this scale in an unusual way. In this song the lead uses lots of trills, slides etc to play almost frivolously along with the rest of the music, rather than doing some kind of epic melodic solo. This suits the nature of the song and also leaves the main melody lines down to the vocals and piano.
The first thing to notice about the lead guitar here is that it uses a lot of trills. These are very fast but quite easy to do with some practice. That makes this an excellent song to learn them with.
Trills are just very fast hammer on / pull off combinations. The first lead guitar part in this song is a trill. Hold the A note on the 2nd fret of the G string with your first finger and pick it. Instantly, hammer on / pull off repeatedly with your 2nd finger one fret above (this note is Bb). All the time keep your first finger on the A. Now all the work is done by your 2nd finger as it hammers and releases the Bb note. This causes you to alternate between the A and Bb notes very fast.
Hammers / pull offs are techniques for sounding out notes using only your fretboard hand. Therefore, after starting the trill by picking the A note - all the rest of the work is down to just your 1st and 2nd fingers blazing away on the fretboard! Remember - the only time you pick any strings with your picking hand is when you start the trill.
Watch this video to learn more about how to do the hammer on / pull off combination, and trills.
Trills can't be easily practiced too slowly. In order to practice them, do them quickly. Make sure your 1st finger is constantly fretting the A note, or you may accidentally mute the string!
After the trills (which are always A-Bb notes in this song), the rest is very straightforward. Slides and vibrato between the 3rd and 4th frets on the B string (D and Eb notes from the Bb major scale) appear next. Just slide up to the Eb and apply a short amount of vibrato as soon as you reach the Eb. Literally waver the string just a little and quickly return to the D for another go! All this is done with your 1st finger.
The rest of the lead guitar is much of the same, and you should be able to do it all without too much difficulty :) If you are feeling adventurous, make up your own melodies for the gaps in the lead using the Bb Major scale as your key!