Using “so” for emphasis is very natural but is often confused with using “really” in some situations. For example, “John was so/really looking forward to the movie”. When do you use really, so, or such? Let’s have a look.
For grammar reference, “really” emphasizes verbs, “John is really looking forward to the movie.”. Use “so” or “really” to emphasize adjectives “John is so/really excited about the movie” and use “such” to emphasize nouns, “It was such an exciting movie.”
To speak naturally, keep using “so” for verbs, “John is so looking forward to the movie”, you’ll be speaking naturally like a grammatically incorrect native in no time.