Bug and Steel types: weaknesses, resistances and Pokémon
Bug and Steel Pokémon take quadruple damage from Fire moves, resist Grass, Normal, Ice, Psychic, Bug, Dragon, Steel and Fairy moves and are immune to Poison moves.
With 9 resistances and immunities against 1 weaknesses, it is a very solid defensive combination.
Bug moves are super effective against Grass, Psychic and Dark and not very effective against Fire, Fighting, Poison, Flying, Ghost, Steel and Fairy. Steel moves are super effective against Ice, Rock and Fairy and not very effective against Fire, Water, Electric and Steel.
To beat these Pokémon, your best pick is Fire moves. Avoid Grass, Normal, Ice and Psychic moves, which deal little or no damage.
There are 5 Pokémon with this combination, such as Forretress, Scizor, Escavalier and Durant.