Here's how you deal with the electric fence:
* Use a Pokémon immune to Electric attacks: The most common solution is to use a Pokémon that is immune to Electric attacks. Ground-type Pokémon like Diglett, Dugtrio, and Rhyhorn are your best bets.
* Use moves that can bypass the electric fence: Moves like Dig or Fly can take you right through the fence.
* Use a Pokémon that can break through the fence: Some Pokémon, like Snorlax, have high enough Attack power to destroy the fence.
* Avoid the fence completely: The gym is designed in a way where you can reach the Gym Leader, Lt. Surge, without directly going through the fence. Utilize the alternative pathways within the gym.
Let me know if you'd like more tips on how to beat the Vermilion City Gym!