I'm installing a new switch and outlet in a previously renovated garage, and I noticed the following:

1. My Klein non-contact voltage tester beeps continuously on all of the metal boxes and surface-mounted MC cable.
2. The voltage tester beeps continuously when I touch it to parts of the wood framing (rafters) and even the door hinges.
3. All of the outlets are showing open ground using a three-light plug-in tester
4. When I use a pin-type voltage tester to check the wiring, HOT to GROUND shows nothing, HOT to BOX/MC CABLE shows nothing. HOT to NEUTRAL shows 120V. Finally, BOX/MC CABLE to NEUTRAL shows nothing.

I've checked all of the boxes, outlets and switches in the garage, and the wiring is fine.

Any ideas for next steps?