Try this small exercise to warm up your power chords 
 a little.

E|-------------------------------------------------|
B|-------------------------------------------------|
G|-------------------------9-9-9-7-7-7-5-5-5-7-7-7-|
D|-9-9-9-7-7-7-5-5-5-7-7-7-9-9-9-7-7-7-5-5-5-7-7-7-|
A|-9-9-9-7-7-7-5-5-5-7-7-7-7-7-7-5-5-5-3-3-3-5-5-5-|
E|-7-7-7-5-5-5-3-3-3-5-5-5-------------------------|
 |                                                 |
E|-------------------------------------------------|
B|-------------------------------------------------|
G|-------7-7-7-------------9-9-9-------5-5-5-7-7-7-|
D|-9-9-9-7-7-7-5-5-5-7-7-7-9-9-9-7-7-7-5-5-5-7-7-7-|
A|-9-9-9-5-5-5-5-5-5-7-7-7-7-7-7-7-7-7-3-3-3-5-5-5-|
E|-7-7-7-------3-3-3-5-5-5-------5-5-5-------------|