I agree with carlos-k. Melodic death metal is great music, but usually pretty difficult to play. It would be very beneficial to first go through Rock (and Blues) to both develop technique and see how much different metal/rock styles actually have in common. To go through blues will especially help your soloing a lot!

For basic metal rhythm practice, check out:
http://www.guitartricks.com/lesson.php?input=16522&s_id=1216
http://www.guitartricks.com/lesson.php?input=16977&s_id=1267

If you want to try some downtuned stuff, you can check out these tutorials:
http://www.guitartricks.com/lesson.php?input=15434&s_id=1069
http://www.guitartricks.com/lesson.php?input=15271