Gigalith's moves (gen 8)

 By level

- Sand Attack (level1)

- Tackle (level 1)

- Harden (level 1)

- Stealth Rock (level 1)

- Power Gem (level 1)

- Mud Slap (level 12)

- Smack Down (level 16)

- Iron Defense (level 20)

- Headbutt (level 24)

- Rock Slide (level 30)

- Rock Blast (level 36)

- Sandstorm (level 42)

- Stone Edge (level 48)

- Explosion (level 54)

By TM/TR

- Hyper Beam

- Giga Impact

- Solar Beam

- Self-Destruct

- Rest

- Rock Slide

- Snore

- Protect

- Attract

- Sandstorm

- Facade

- Weather Ball

- Rock Tomb

- Sand Tomb

- Rock Blast

- Round

- Bulldoze

- Stomping Tantrum

- Earthquake

- Substitute

- Endure

- Sleep Talk

- Superpower

- Iron Defense

- Power Gem 

- Earth Power

- Flash Cannon

- Iron Head

- Stone Edge

- Stealth Rock

- Heavy Slam

- Throat Chop

- Body Press

By breeding

-Autotomize

- Curse 

- Gravity

- Take Down

- Wide Guard

By tutoring

-Meteor Beam

By transfer from other generations

- Block 

- Confide

- Double team

- Frustration 

- Hidden Power

- Laser Focus

- Lock-On

- Magnitude

- Nature Power

- Return

- Rock Polish

- Rock Smash

- Secret Power

- Strenght

- Swagger

- Toxic

Moves listed in italic can't be used in gen 8

Source :

- Bulbapedia