What I wrote back in 2017 in the "What was the last movie you saw" thread:
THEM! (1954) -- first of the giant bug movies and still probably the best. The black and white cinematography and the gravitas of James Whitmore, James Arness and Santa Claus -- er -- Edmund Gwenn help carry the premise of ants made giant by radioactivity. Terrific, creepy early sequence with a little girl found wandering in the desert and her reaction to the noise the ants make. The movie also offers quick glimpses of actors early in their careers who visited our living rooms for the next few decades: Richard Deacon, William Schallert, Dub Taylor, Leonard Nimoy and Fess Parker.
That is so subtle compared to most monster movies of the time, that it really strikes home.