Metal phone cases are potentially unsafe when plugged in. Plastic cases are much safer. ⚡

While it’s true that neutral – which the metal cases are connected to normally carries no voltage and that USB positive is a safe 5 volts, transformer insulation sometimes fails and some cheap chargers like inexpensive camping lamps use capacitive droppers that are fully referenced to 120 volts.

Most of the time, transformers are safe and there is no concern. UL and Intertek standards require good separation and proper insulation with high voltage breakdown testing to ensure that you don’t get shocked and die.

But why risk it?