Guitar Teachers

I have been playing guitar for about 3/4 years and i seem to be getting faster playing but i cannot seem to pick up any theory.

Will a guitar teacher help me with the theroy so i will be able to write good lead guitar lines that fit in with a Key/ Metal riff. Would it also help me progress in being able to shred faster?

Some teachers might be able to help you in this field that you mentioned. However, when you about the key its not that difficult really. Let me give you some tips to help you

imagine a full circle C key has no flats or sharps count five which will become G with one sharp F sharp now count five from G which will become D with two sharps and so on. This is known as a circle of fifths as you are counting up in five.

Metal guitarist tend to use power chords with a 5th in so you might see E5 or G5 you can play any solo using any type of scale not just lets say E minor you might want to use Dorian scale or another choice that sounds hard.

Move on a little now and take a look at this chord progression

G,D and Am this is G major key so why is it G major. Well you are starting on G as the main note so far so good. Now lets change it Am, C Em and D. So what key would this be? Have a think... it would be once more in the key of G why

lets look deeper at this

G, AM, BM, C, D, EM and F sharp dim (ignore the last one for now)
as you can see that Am is in the key of G also C major, E minor and D major

Okay so far. Keep up at the back

D, C E minor what key is this in?

G key

Bminor c minor D major work this one out for yourself it not G key this time. Stuck

Well it is in the key of A lets have a look will B minor fit well it fits as it is the second note to A will C minor fit yes that would be the third note in the key of A major and final one D major that is forth note of A major. Remember how we worked the last on out in the key of G major
lets do that

A Bm Cm D E Fm and G sharp Dim
1 2 3 4 5 6 7

The major is work out like the following I am about to show you

Major, Minor, Minor, Major, Major, Minor and dim remember this and you can workout what key you are playing in even if you using power chords or not simple.

Will go on with some more but this will give you a huge start now and if this has helped anyone let me know. If you can't understand it yet then let me know as I try not to go too deep with this chaps question

Back to Magus' question. The answere is yes, a teacher can always help to improve the playing, no matter he teaches you jazz he'll surely help. THe real question is what you want to learn. A teacher must'nt only teach you the theori, he can give you practices so you control you fingers better or to improve your phrasing by teaching you different scales which are supposed to help you on the way.

Tragically a lot of these metal players only go for speed when soloing or "heavyness" while backing, and that is what leaves them to not develop anymore when they reach one certain point. I hope you're not one of them, for you own sake.

But good luck and once again, of course can a teacher help you - it is up to you what you want to learn.