Prophecy is essentially a mutant or monster story.
https://en.wikipedia.org/wiki/Prophecy_(film)#Plot
https://www.denofgeek.com/movies/prophecy-1979-a-bad-monster-movie
https://macguff.in/macguffin-spotlight/the-tomb-of-terror-prophecy-1979
https://movie-monster.fandom.com/wiki/Katahdin
https://moviechat.org/tt0079758/Prophecy/58c7355f5ec57f0478fa1e28/Manbearpig
https://www.reddit.com/r/southpark/comments/ex2dm2/is_the_design_of_manbearpig_based_off_of_the
Perhaps MBP could potentially become its own monster story.
https://en.wikipedia.org/wiki/ManBearPig
A composite creature or mutant beast on the loose movie, could possibly feature something like MBP.
https://southpark.fandom.com/wiki/ManBearPig_(Character)
Annihilation could be considered to be a monster movie of sorts.
https://en.wikipedia.org/wiki/Annihilation_(film)#Plot
An ET entity can create composite beings or mutants and mimic people and things.
Annihilation (2018) - The Mutant Bear Scene https://www.youtube.com/watch?v=Mg0bvyIEHcs
ANNIHILATION (2018) Ending Explained + Analysis https://www.youtube.com/watch?v=d94h-PKyh64 , https://www.youtube.com/c/FoundFlix/videos
Annihilation Explained https://www.youtube.com/watch?v=zy5TsNHlSDU , https://www.youtube.com/c/AltShiftX/videos
https://en.wikipedia.org/wiki/Monsters_(American_TV_series) , https://www.youtube.com/watch?v=8Px43Z748UI , https://bloody-disgusting.com/editorials/3693973/monsters-still-one-time-best-horror-anthology-shows-tv-terrors
11 Blood-Curdling 80's Monsters TV Series Episodes Explored - Epitome Of Creature Practical Effects https://www.youtube.com/watch?v=Vba_xLctsw0 , https://www.youtube.com/c/MarvelousVideos/videos
Top 10 Scariest TV Monsters https://www.youtube.com/watch?v=vgvZBcSQYQ0 , https://www.youtube.com/user/WatchMojo/videos
DEVO - Monsterman https://www.youtube.com/watch?v=NVrijrV5cYs , https://www.youtube.com/c/DEVOvision/videos