The reason for this is that the metal suit is a closed surface of conducting material. The electricity is conducted through the material, and only ever skims along the surface of the outside of the suit. There is no current on the inside of the suit at all, so the fact that you’re touching the inside by wearing it doesn’t matter.

Now, that being said, this does NOT mean you won’t feel heat, like an above poster erroneously mentioned. The electric currents on the surface of the metal will heat it based on how much resistance there is, the strength of the currents, and the length of time the currents last. In a lightning strike, the amount of current is ENORMOUS, but the time is also incredibly short; it’s kind of anyone’s guess as to how hot it would get. (The kind of metal would play a part here; silver is a better conductor than copper, which is about 10 times a better conductor than steel.)

On a summer’s day, wearing a suit of armor, you will get very hot. To say anything else is simply ridiculous.

PS. The shielding provided by a suit of armor can actually be created much more easily. Rather than a several hundred pound suit, why not wear a wire mesh suit? It is close enough to being a solid conductor that you’d be shielded well enough. See the ArcAttack link.

But of course you can dissipate the electron flow in other ways, with grounding, and with heat, if the metal gets hot enough then electricity wont flow though it

Though ofcourse if you are touching the metal, then you will shock, even if you are grounded because you will basically be one big grounded conductor