OK, I've been playing guitar for a year and a half, and im in 2 bands, im lead guitarist, but i have a dilemma. I cant break out of Pentatonic Soloing. i need help! Can anyone suggest me other scales? I play mostly Hard Rock and Heavy Metal, like, Slipknot, Sabbath, Metallica, and the like. I NEED HELP PLEASE
Learn regular diatonic scales.

I'm assuming you'd rather learn minor than major, so learn minor.

Make sure you know how minor scales work and why they have a major dominant chord and how it's derived, etc. It's good to understand how the scale works, it'll give you more control over it.

Natural minor: 1 2 b3 4 5 b6 b7
Harmonic minor: 1 2 b3 4 5 b6 7

Those two scales pretty much walk hand in hand.

In the key of A Minor:
A B C D E F G# A
Learn the major scale and its modes. Practice them in every key and ingrain them into you. Its not that hard to transistion from the pentatonic scale to the major scale and its modes. Its just a matter of adding in 2 extra notes to whats already there.
I agree with the above answers. Modes can be overwhelming though, so be patient and take small steps. Dont go in thinking you can get them all down in one day. Like one_vision said, natural minor and harmonic minor for starters, they just add 2 new notes to the pentatonic scale. Then if you feel like youve got those, try phrygian mode. Its also pretty simple, less finger stretches even then natural minor. Its got a dark, haunting sort of sound, too, which you might like given the bands you listed.
Phyrgian scale. A lot of heavy metal players use it, and so does Slash. It's that scale with a really spanish-type feel.

In the key of E Minor, which is:

E F# G# A B C D E

It would be:


You just lower that second note in the scale, pretty easy.
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I think its best to actually learn the major scale and all its modes. Because you might learn Phrygian and then play it over something and it doesn't sound dark in the slightest. Since you don't know about modes yet I wont go into detail here but essentially the Phrygian scale formula played over chords which don't emphasise it will not yield an authentic Phrygian sound. A little bit of time spent getting to know the modes and how they apply will open up many doors for you. I agree with everyone saying learn Phrygian, as its killer for metal...but at the end of the day Phyrgian isn't anything but a major scale starting from the 3rd degree.
If you are really interested in getting to know your scales etc this is the best bit of advice I can give you. Instead of learning the scale formula for one mode and then getting all confused when you try to work it back. Better starting off with the basics and in a short time you will understand it. Modes aren't really so hard to grasp as they are made out to be. Check out some stuff about modes either on this forum or elsewhere on the net and then go search for Vinnie Moore Modes Lesson on youtube. He gives a pretty good explanation.
Your problem isn't with boxes per se. Most likely someone showed you the pentatonic
scale, told you "use these notes to solo", and that's all you've been doing without
really understanding the notes other than through guesswork and learning some tabs.

What everyone else has said: learn the major scale and how it's a musical foundation
for most everything.

I'd aslo suggest you take a simple ii7-V7-I7 progression and learn to solo over it. You
won't be able to use the pentatonic minor (in the way you're used to). It's the most
dead-simple progression for mainstream music jamming. Yet, someone who just
knows pentatonics will likely have trouble with it. It'll force you to expand your