Like Mr. Miyagi said... best way to not get hit "No be there" .
The in-universe logic is at least consistent. All of the things the MC uses, from his armour and weapons to his clothing, are technically a part of his weird supernatural body, and thus respond to its weaknesses no matter what form its been turned into.
Ya I was going to point out this same thing. Anything created from the MC's body will have all the properties of the target object but at its Core it will still stay connected to the MC and be a part of him. It comes more from the magic part of the monster abilities rather than the science part.
So no matter what he creates to insulate himself against electricity as long as it was produced from his own body it will react to the energy and explode. even if its a golden Lightening rod or a Giant Block of Dense Wood/Asbestos around his whole body.
I was also trying to think of a solution to this same issue months ago fearing we might have to face Met someday. Eels, rays or jellyfish were no help. But I also am all for MC going around absorbing Exotic Monster corpses, a little bit of corruption can't be that bad. The Lightening monster's crystals did look like they could be a useful.
Unlike kryptonite tho electricity I really think will help mc in the future.Electricity rn feels like a fuel which mc just can't control.
I also suspect the solution to the problem of electricity is MC having greater control over his body so he can in a way have absolute command over his cellular structure dominate the smallest part of his being and force it to retain its shape even while being bombarded with energy ... absorb the energy like a little bio battery so it can be reused by the MC or at the very least redirected with minimal damage.
The way electricity makes MC's cells expand and explode reminds me of how the Alien goo reacted to heat in that old "Evolution" movie. Sudden explosive growth.