I've been learning how to play the guitar and I have a teacher. I'm learning scales, chords and how to read sheet music. I'm curious what is the best technique to practice to advance quicker at the guitar like which scales, techniques, etc.

metal? power chords. learn to play power chords very fast and very well. its easy...

just try songs starting with people who started metal, black sabbath, metallica, ext. look up tabs, you learn songs and generaly get better a the guitar.
they best way to play guitar is by starting out on blues, hard as hell, best way to learn, teachs rythem and how to put soul into what you play, zakk wylde would be one of those people who incoporates both metal-blues in his playing