This signature tune by AC/DC is written in the key of E. It begins with a simple E-D-A chord progression with a lead fill built off of the E pentatonic minor. The lead fill may take a little practice to get up to speed. The riff ends with a “walk-up” on the low E string while alternating with the B note on the 2nd fret of the A string. This part requires a little bit of flexibility in your fingers.
Here’s the 1st lick from the solo: