This is the main guitar for the song. It has all the main riffs and the solo too. There is also a second guitar, which we'll look at separately. That is easier and better suited to beginners, but doesn't contain all the main riffs.
Intro
Use a clean sound (no distortion) and pick your way through the following chord progression:
F#m - E sus4 6th (also a reversed A major chord) - B7 - Play the F# note and slide to G sus2 - Play the G note and then Am - end on the G note again, then repeat.
The fingers (dot colours) shown here are very important for getting smooth chord changes!
Verse
Hit the distortion. It's metal time...
F#5 - double stops (palm muted) - A5 - muted strike - double hammer - 2 more double stops - Low E (palm muted) - F#5 - Low E (palm muted)
Repeat that sequence again until just after the muted strike. Then play B5 - double stop - B5 - muted strike - D5 (the other guitar strums this repeatedly).
Melody
The melody is played by picking through chords on the 3 highest strings:
A major - E major - B major - F#m - A major - C#m - B sus2 - D sus2
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2nd Verse
This is almost the exact same as the intro. However you need to play it all using palm muting this time!
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All these guitar parts are repeated throughout the song to the end. There are only 2 parts which we have left out and these are:
Solo - Leave this unless you have the skills. It's typical Megadeth - i.e. awkward. Then progress to play another song riff. This riff is very similar to the verse riff, except up by 2 frets (and shorter). The starting chord is G#5.
Outro - This is just more of the same stuff we've already seen so far. However, it starts with a harmony. While this guitar plays through the melody, Guitar 2 is playing another melody with different notes.