Watch the I-IV Power online guitar lesson by Brad Carlton from Chord Studies: Power Chords Vol. 1
This is another I-IV progression using power chords, this time in the key of G. Again we are using the common tone principle of previous examples. Notice with our G5 chord, we've only got one five in there and it's the top voice, giving it a unique sound. Then we move down to the C5 creating a melody by moving the D note down to the C.