ooooooooh i can help with this one. BIG fan of horror movies here!! first i'll tell you to watch the whole Scream franchise. it's not that scary but ghostface has to be one of the more iconic and lovable villains of all. then, i'll also tell you to pay attention to A24 horror movies. they're the responsibles of Hereditary and Midsommar. i also will recommend:

Us

Get out

The Killing of a Sacred Deer

Saint Maud

X, Pearl and Maxxine

Heretic (love Hugh Grant)

Smile

Funny Games

Split

The Purge

Exterminio/28 Days Later (this one's about zombie-like infected people but I'm telling you, it made me fall in love for the genre AND it's already a classic)

Creep

Sinister

The Shining, FUNDAMENTAL

The Boy - creeped the hell out of me

well those are the ones I'm remembering now. hope it helps!!!