So and such are both used to express extremes. They are often used in exclamations (and they are so useful!).

So
=> Use "so" before an adjective (without a noun)
=> Use "so" before an adverb

Examples with so:
▶ Andy is so good at tennis! NOT: Andy is so good tennis player!
▶ Angela's baby is so cute!
▶ Jay's new painting is so beautiful. He's so talented!
▶ Your house is so beautiful.
▶ That was so kind of you!
▶ John works so hard.
▶ Kristen looked so lovely in her wedding dress.

Such
=> Use "such" before an adjective + noun
=> Use "such" before a noun

Note that when the noun is singular, "a" or "an" comes after "such."

Examples with such:
▶ That was such a scary movie! NOT: That was so scary movie!
▶ That's such a cute baby!
▶ You are such a good friend.
▶ Phil is such a hard worker.
▶ You prepared such a delicious meal.
▶ This project is such a headache!
▶ Why do you carry such heavy bags?