Movie monsters typically resemble real-life animals in some way, or in the case of movies like Kong: Skull Island they look just like giant-sized versions of real critters, making them terrifying in a more realistic way.
Viewers assume movie monsters screech, scream and roar like their normal-sized cousins, so filmmakers keep their voices pretty much the same, but according to scientists these creatures would make a sound like you've never heard before.
This video by The Verge examines the sound that should be coming out of a giant movie monster's mouth with a little help from paleontologists Dr. Thomas Williamson, David Weishampel and Dr. Stuart Sumida and biology professor Philip Senter.