Steel Beam is learned by 48 species by machine and 52 by tutor

Effect, in PokéAPI's words

“Inflicts damage, and the user takes damage equal to half of its max HP, rounded up.”

Who learns it

71 species in all, 2 games

Scarlet and Violet: 48 species

Species	Method	Level
Magnemite	Machine
Magneton	Machine
Mew	Machine
Forretress	Machine
Scizor	Machine
Skarmory	Machine
Nosepass	Machine
Beldum	Machine
Metang	Machine
Metagross	Machine
Registeel	Machine
Jirachi	Machine
Empoleon	Machine
Shieldon	Machine
Bastiodon	Machine
Bronzor	Machine
Bronzong	Machine
Lucario	Machine
Magnezone	Machine
Probopass	Machine
Dialga	Machine
Heatran	Machine
Arceus	Machine
Excadrill	Machine
Pawniard	Machine
Bisharp	Machine
Cobalion	Machine
Klefki	Machine
Solgaleo	Machine
Magearna	Machine
Corviknight	Machine
Perrserker	Machine
Cufant	Machine
Copperajah	Machine
Duraludon	Machine
Zacian	Machine
Zamazenta	Machine
Tinkatink	Machine
Tinkatuff	Machine
Tinkaton	Machine
Varoom	Machine
Revavroom	Machine
Orthworm	Machine
Kingambit	Machine
Iron Treads	Machine
Gholdengo	Machine
Archaludon	Machine
Iron Crown	Machine

Sword and Shield: 52 species

Species	Method	Level
Magnemite	Tutor
Magneton	Tutor
Steelix	Tutor
Scizor	Tutor
Skarmory	Tutor
Mawile	Tutor
Aron	Tutor
Lairon	Tutor
Aggron	Tutor
Beldum	Tutor
Metang	Tutor
Metagross	Tutor
Registeel	Tutor
Jirachi	Tutor
Bronzor	Tutor
Bronzong	Tutor
Lucario	Tutor
Magnezone	Tutor
Dialga	Tutor
Heatran	Tutor
Excadrill	Tutor
Escavalier	Tutor
Ferroseed	Tutor
Ferrothorn	Tutor
Klink	Tutor
Klang	Tutor
Klinklang	Tutor
Pawniard	Tutor
Bisharp	Tutor
Durant	Tutor
Cobalion	Tutor
Genesect	Tutor
Honedge	Tutor
Doublade	Tutor
Aegislash	Tutor
Klefki	Tutor
Silvally	Tutor
Togedemaru	Tutor
Solgaleo	Tutor
Celesteela	Tutor
Kartana	Tutor
Magearna	Tutor
Stakataka	Tutor
Meltan	Tutor
Melmetal	Tutor
Corviknight	Tutor
Perrserker	Tutor
Cufant	Tutor
Copperajah	Tutor
Duraludon	Tutor
Zacian	Tutor
Zamazenta	Tutor