Dave Davidson, (from the band "Revocation"), filmed a quick lesson at the Guitar World studios covering some cool pentatonic and modal concepts for Thrash...
The pentatonic scale is the one scale that just about every rock, metal, blues, jazz and country guitar player is well familiar with.
These five-tone scales—both the minor and major forms—sound great and fall easily on the fretboard, earning them their prevalence in all popular guitar-driven musical forms. One of my favorite things to do when writing riffs or soloing is to take a pentatonic form in one key and superimpose it over another.
The result is often a sound that combines the familiarity of the melodic shapes and patterns with the ambiguity or unusual harmony created by this twist on the conventional approach to using pentatonic scales.