2. Surf along the coast to Cerulean City. Once you have the Rainbow Badge, you will be able to use Surf to travel across water.
4. Travel the Pokemon Mansion road to the west of Saffron City and challenge the Gym. Lt. Surge can be tough opponent so make sure your team is strong and healthy before engaging in battle.
5. Defeat Lt. Surge. Lt. Surge specializes in Electric-type Pokemon, such as Pikachu, Magneton, and Voltorb. Be sure to use Pokemon that are resistant to Electric-type moves, such as Ground-type Pokemon.
6. Obtain the Thunder Badge. After you defeat Lt. Surge, he will give you the Thunder Badge. This Badge will allow you to use the HM move Thunderbolt and enter the next Pokemon League Gym, which is located in Celadon City.