how do u know what root note to start on in a solo also whats a good scale to lrean to play heavy metal

Intersting question.

SOLO: There is no root note as such, it shoud be what ever you hear in your head, whilst listening to the,
rhythm section, or it could be sponataneous. It's good to stick initially with the key of the song if your new to soloing, or learn the blues scale, you can play this scale with almost anything and it's good fun.

SCALES: I'm no specialist in heavy metal music, but assume most are in a major keys? if it's the guitar, a lot of  music like metal is in the key of A or E, but I personally think the key should be either be one that makes it easy to play and, or a key that the vocalist is best suited.

Hope this helps

Denis

Yeah, I agree with Denis.  The blues scale is the place to start for any kind of rock soloing... and it only has 6 notes 

Here's a good link to start with:
http://www.12bar.de/soloscal.php

Root notes ,, you can go by the root note of the key of the song, like if in A you could start the solo in
A.. but if the chord is not A, or a chord that clashes with the  A note, it probably will sound off.  The other way to do the root note thing is look at what chords are being played throughout the solo section, look at what notes make up each chord then solo in and around those notes as those chords are being played.

Lets take the key of A and the solo is  in the chords F, G, A,  you could start on the note A because it is in the F chord or you could play the notes F or C ( F chord is F,A,C,) so  all three would work well as a starting note just for the F chord only though. The G chord will hit and since G is   notes G,B,D, notice A is not in this chord so it might clash with it , G,B or D will work fine.Same with A chord, I am gonna use the minor chord  so the C notes match up so it would be A,C,E any of the notes will work... now scales..

look at the A natural minor scale.  ABCDEFGA  hmm  see the notes from the chords  above are all in this scale.
you could learn the A minor scale and play it well over  chord progression in  A minor.

I also agree the the blues scale is very useful and almost every guitar player out there that is any good knows it very well.

i do know the blues scale up and down the neck but just have a problem with where to start with solos i think that will help thanks too all of u guys

The blues and the very similar minor pentatonic scales are must-knows in any rock guitarist's bag of tricks.  Most every rock guitarist you can think of relies pretty heavily on drawing from these scales (Angus Young is an extreme example, but even legends like Rossington, Clapton, Hendrix, SRV, Gilmour, the list goes on).  If you're going to use the blues scale with the one "blue" note in it, just be careful where you're striking that one.  Guys like Vaughan or B.B. King have an incredible feel for where to lay it down, but if you're not sure, it can end up making you cringe.  As for starting with solos - listen to your favorite guitarists.  I'll use "I Shot the Sheriff" as an example, a pretty basic studio version, but live you'll see Eric really have extended stuff and most of it takes place in the Gm Pentatonic - so maybe you listen to a lot of that kinda stuff to get a feel for how to lay down a funky solo in Gm.  Staying in that vein, check out, say, "Texas Flood" for a little more laid back, swingy feel, and then, say, "Smoke on the Water" for that more traditional rock solo.  All three tunes rely heavily on the same scale, but all three tunes are gonna produce drastically different feels.  Basically, what I'm getting at, is to get a feel for the music you're playing and the direction you want the solo to go in.  Don't necessarily copy your influences, but feel free to draw from them.  That's what they're there for.

hey I love to play like heavy metal stuff down in drop d 1 step, (Cgcfad) its a place for bands like 'As I Lay Dying' or early 'System of a Down' albums. Both are huge inspirations for me, and I find that most of the solo's are started by a note in the range of 7 to 12 on the a or d string, (g or c if tuned down.) they then build their way up and down a pentatonic scale. try learning some solo's off of the album, "An Ocean Between Us" by As I Lay Dying and you'll really get my point. Its usually a note that makes an appearance in the main heavy riff every once in a while.

hope I could help

Jheormy

learn as many scales and how to use them if you want to be excellent, spend lots of time with the blues, and ext blues scales , major and minor.  Learn how to do the shift position for major/minor.. and  if you really want to get with the program..... study your arpeggios ...major , minor, diminished, augmented, and variations  with and without  the 7th's in there.. practice them with flatted notes like flat 5 or 6 ect.    This will give you knowledge of the neck in not only linear ,but vertical motion simultaneously.    Learn your chords.  get used to working with 9's 11th's , 13th's . this will bring about tones and taste that lots of guitar players never get.

dont have a clue....musy=t have roots growin out my ears lol

Thanks for the info on the blues scale and ill try the a minor.  Since I don't know a single scale it gives me a place to start.  - tend to just have a mmelody in my head and find the right note that way... If it sounds good - sweet!  Though that is obviously less efficient lol. Its almost like colateral learning lol.  Thanks again