Yeah, don't abandon the blues altogether. There's some magic and power to those pentatonic scales, and they're often useful if you're in a situation where you have to adlib a solo. They're also a great basis for actual riffs. So, stick to your blues roots for they are the roots of rock and roll.... amen.
I do, however, think it's a good idea to expand your style into involving elements from all sorts of different musical traditions, so I don't see the problem in you doing some minor scales as well, or perhaps something from non-western traditions. I think some of the Arabian-sounding scales are really cool in certain types of metal, especially the slower more doomy stuff.
So, like the others have said, shop around and let yourself be inspired by other guitarists. Try to also look outside of metal, as there are some interesting things out there too. Let yourself be inspired and just play - go with the flow. That way you'll develop a style of your own.
In addition to the three amigos, Tony Iommi, and Slash, you should listen to Dimebag Darell, Richie Blackmore, Chuck Schuldiner, K.K. Downing, Glenn Tipton and Jimi Hendrix. They all have unique personal styles that are inspire both by the blues and the more classical minor-scale style as well as other musical tones and traditions.
I play a Gibson SG too, and, personally, I think it's a very versatile guitar. I've seen it used in everything from jazz to death metal, so it's not a question of a style of music being unsuitable for that guitar.
