Here's 2 chord progressions you see a lot in the music of punk, alt. rock, & metal;

1) take a major bar chord (or power chord)and move it 3 frets up or down the neck (this is the distance of a minor 3rd).....ex. C Eb

2)play a major bar chord off the 6th str., move it to a major bar chord off the 5th str. 1 fret up.(or vice versa)
ex. G to Db (this is known as a tri-tone)

Rock On!!!