photo by MATEOMTB

If you are into metal, jazz or funk, then you'll need to know how to stack thirds.

People use this technique when adding vocal harmonies, and it's a good way to get up and down the neck. Thirds also dictate whether a chord is major or minor, so you can imply that a chord is being played even when your band is only playing power chords. If that doesn't make sense now check out the videos and it will.