Steel-type Pokémon

Bug/Steel-types

Immune to Poison attacks; strong against Bug, Dark, Dragon, Ghost, Grass, Ice, Normal, Psychic, and Steel attacks; weak against Fire attacks

Forretress
Scizor

Electric/Steel-types

Immune to Poison attacks; strong against Bug, Dark, Dragon, Electric, Flying, Ghost, Grass, Ice, Normal, Psychic, Rock and Steel attacks; weak against Fighting, Fire and Ground attacks

Magnemite
Magneton
Note: In Red, Yellow and Blue Versions, Magnemite and Magneton are pure Electric-types

Steel/Flying-types

Immune to Ground and Poison attacks; strong against Bug, Dark, Dragon, Flying, Ghost, Grass, Normal, Psychic and Steel attacks; weak against Electric and Fire attacks

Steel/Ground-types

Immune to Electric and Poison attacks; strong against Bug, Dark, Dragon, Flying, Ghost, Normal, Psychic, Rock and Steel attacks; weak against Fighting, Fire, Ground and Water attacks