The others are right. You shoudn't be too worried about strings right now but about better equipment. I would defifetly recomend a better amp. Maybe a Marshall or a Fender. I use both. If you don't want to get a new guitar you could change the pickups out with EMG's or Seymour Duncans, both have a good metal sound if you get the right ones. For string gauge I would recomend 10-46's. They allow you to be heavy & to have a great lead as well.

Good Luck!!!