One factor is the use of suspense. If a movie can keep you on the edge of your seat, like in 'Get Out', it's effective. The slow build - up of tension makes the scares more impactful. Another is the use of relatable fears. For example, in 'The Babadook', the fear of a single mother losing her sanity while dealing with a strange presence is something many can relate to.
Effective scary movie stories usually play on our primal fears. Fear of the dark, as seen in 'Lights Out', is a common one. The element of the unknown is also crucial. In movies like 'Paranormal Activity', we don't fully understand what is causing the strange happenings. And strong character development can make the horror more personal. In 'The Others', the mother's love for her children and her fear of losing them in a haunted house situation makes the story more engaging.
A good scary movie story often has a great villain or monster. Take 'Jaws' for instance. The shark is a menacing presence throughout the movie. The music also plays a huge role. In 'Halloween', the simple yet effective theme music adds to the scariness. Additionally, the setting can create a lot of horror. An old, abandoned asylum like in 'Session 9' gives an immediate sense of dread.