Watch the The VII chord online guitar lesson by Matthieu Brandt from Songwriting on Guitar
While we're in the business of changing the original chords in our major key, we can take a look at the one chord we have not used yet: the chord on the seventh degree of the scale.
In its original form this chord is a diminshed chord. It contains two flatted third intervals on top of each other. Which makes it have a diminshed interval on top of the root: not a perfect fifth like all the other major and minor chords. This makes for a very unstable sound that is not used in major harmony.
By raising this diminished fifth one half note, we end up with a regular minor triad. This one wae CAN put to use. Many composers even change this chord to a major triad, by also raising the flatted third of that chord.