By crazy Metal I mean rhythms like these

Stronger Than Hate by Sepultura

http://www.youtube.com/watch?v=0UbS7puncnk

Agoraphobia by Protector

http://www.youtube.com/watch?v=P0jumiAlsjQ

What Dwells Within Bolt Thrower

http://www.youtube.com/watch?v=RXvJ_qVe450

Destruction System by Morbid Saint the first 2 minutes

http://www.youtube.com/watch?v=hd12SaKkC_A

Capture The Flag by Sodom first at 1:45 seconds

http://www.youtube.com/watch?v=mCk7vsWMq90