it's all in the manner of taste and appreciation.. you are making music to connect to people.. and also you are targeting what type of people or listeners you want to interact right.. for example, right the given example stated above, kirk hammett.. kirk hammett is a rock/ metal guitar player.. siguro naman hindi niya tinatarget na makapagdraw ng attention sa mgA chamber or classical musicians diba.. he interacts with the type of people who's into the similar type of music that he is playing..
secondly, what sound good to you might not sound good to others ear.. as being musician, mula nung nagsimula tayo hanggang ngayon, ibat iba tayo ng pinagdaanan and you must admit it..kaya nga all of us are unique when in terms of music eh.
in my experience, a guitar solo/melody or instrumental is really a matter of personal choice..in my experience going into recording, a guitar solo is a part of music na hindi nalalayo sa vocal melody or lyrics, they are both needed to be written even you are just trying to jam or improvise with it..
a guitar solo is a very big voice.. you are giving a certain kind of feeling with it, send message and most importantly, give the meaning of the music itself through the notes you play, the way you sound and the way you play it. You have to stand every note you play. You didn't know exactly kung anu yung tumatakbo sa utak ng mga players when doing a solo, iba iba tayo ng mararamdaman kapag nandun na tayo sa moment na iyon.
and lastly, the most important thing,, RESPECT.. if you want to be respected by your fellow musicians, try to respect them also.. Be A Low Profile Individual..thanks..