The only time I ever use a metronome is to see what speed i'm up to, I never use it to increase speed. If your playing shreading patters just practice them slowly and let them grow. As for picking, try what you feel comfortable with and also have a go at learning other ways of doing it....if you work from tab like I do this is quite easy to do....that way you have your own style plus something else to draw on if you want to.