Prog rock guitarist and teacher with a passion for Music Theory applied to Guitar.
Intervals are usually one of the first thing explained in music theory book and websites - and there's nothing wrong with that, except for the fact that they are only explained "in theory" With this I mean that, more often than not, no practical applications for intervals are given in those books or websites: intervals are something you are supposed to study and they will be useful in the future. Kind of like the broccoli your mom made: they tasted horrible but hey, "they are good for you" :-)
Result: musicians get the impression that music theory is not really useful for people who actually want to make music, and get back to play the same old pentatonic scale.
Well, as it happens, it takes just a little bit of imagination to find a practical application for intervals that even a beginner can put into practice immediately. It also happen to sound awesome. I see people like John Petrucci using this kind of trick often in their solos (you can check out the John Petrucci "Pull Me Under" solo here) - and if it's good enough for Petrucci, it's good enough for me.
So without further ado, here's a video that explains how to make your solos way more interesting using one of the most "boring" concept in music theory: intervals. Only, once you apply them they are not boring anymore :-)
That should be enough to keep you occupied for a while with your guitar - and remember that on the video I applied the concept only to one possible interval, the perfect fifth. I leave to you to use the other intervals and discover what kind of sounds you can get from them. Enjoy!