I've always enjoyed sci-fi, and some of the old 50s B movies were great fun.
I think my favourite has to be Them! - it has everything. If you watch it carefully and compare it with Jaws, in many respects the monster reveal is handled the same way. And of course, it had Edmund Gwynne in the scientist role. And if you look carefully, you'll see a few people who became much bigger names later on - James Arness, of Gunsmoke fame, Fess Parker (later best known for Davy Crockett on TV), and in a very minor role (uncredited) as an Army Telex Operator, Leonard Nimoy, who became best known as Spock in Star Trek, of course.
Great fun.
You should try the Incredible Shrinking Man (1957). I'm sure Marvel got some of their Ant Man ideas from that.