Electronic Box Shielding ?

Exhaulted Electronic Wizards:

The third in my series of three (maybe dumb) questions. :-)

With chopper stepper drivers, computer electronics, etc. I'm
convinced there is a great amount of electomagnetic noise
created. I'd like to contain and master it. :-|

SO, if I build a box for my electronics and ground this
box will it supress electromagnetic energy escaping the box?
I'm sure it can so now for the real questions, does the box
need to be steel, i.e. magnetic, or will aluminum work as
well??

Then if I connect the ground from this box to a step up
transformer and plug it into the wall, can I make my electric
meter go backwards? Only kidding in this paragraph. :-)

Thank you for your help.

Hugh Currin
Klamath Falls, OR