This article builds upon the concept of the three layers of a song. If you are not aware of this concept please read this article here first.
<Sometimes a riff played in the opposite space of the melody such that they "dovetail" into each. Note the following:
(Riff ending with B)Don't wanna be an American idiot.
(Riff ending with Gb)Don't want a nation under the new media.
(Riff ending with B)And can you hear the sound of hysteria?
(Riff ending with Gb)The subliminal mind F### America.
So we could start the riff pattern as A-B-A-B and the same pattern is used by the melody. So together we get the following:
A A' (pronounced A and A prime)
B B'
A A'
B B'
Also note that the riff makes it a perfect place to use the "me first" density layer pattern. The guitar plays and then the band jumps in after the first riff completes.