Anything conductive will offer some protection. However a faraday cage has to be 100% to provide complete protection. The items inside also have to be insulated from the shield.
“faraday cage “
Technical sounding term people talking about EMP love to toss around, makes them sound technical, but a farady cage against a partical wave has zero protection. E
ven when the military protects against EMP they do so because of direct nuclear blasts from 1/4 mile away and there isn’t a pinhole to be found in the welding. That’s right, welding. Their buildings are plated in 1/8 steel and welded and tested such that not a single pinhole is to be found. Of course, read what I wrote: Nuclear blast. They are protecting from a blast from a warhead detonated nearby, not high altitude.