Watch the Mixed Mode Harmony online guitar lesson by Matthieu Brandt from Songwriting on Guitar
Many modern songs don't stick to using just one form of harmony; major or minor. Mixing them up will give the composer an extra set of moods to toy with. Introducing chords from the minor scale with the same root as the major scale you are using in your composition and vise versa, will give you this mixed mode sound.
In general these songs will have a rough edgy sound, wether it's in one section of the song or throughout the composition. The chosen melody needs to take the underlying chords into account. By doing this consciously you can stress the rawness or obscure it.