I’ll try to give you easily streamable/rentable options. A lot of great indie horror is hard to find. Possession may not be streaming anymore sadly..
Classic: Rosemary’s Baby, The Thing (any John Carpenter), The Shining, Sixth Sense, Halloween, Evil Dead, Possession, Suspiria, could go on forever…
Folk: Wicker Man, The VVitch, A Field in England, Saint Maud, Blair Witch Project, any Ari Aster/Robert Eggers
Camp/Slasher: Ma, V/H/S, Dead Ringers (loads of cronenberg), Henry Portrait of a Serial Killer (challenging but rewarding watch, great performance), Terrifier, Bone Tomahawk
Cautionary Tale: Get Out, The Killing of a Sacred Deer, The Menu, Talk To Me, The Night House, Goodnight Mommy, Barbarian, Possessor, Watcher
Could list a lot of great foreign especially Korean and Japanese stuff but I find subtitles difficult when viewing on an outdoor screen.
I’ve got a crazy long list on Letterboxd lol