そうに / そうな

そうな and そうに are the "looks" そうだ in front of another word: そうな before a noun, そうに before a verb. They attach where そうだ does, to a verb's ます-stem or an adjective's stem, with an い-adjective dropping its い.

The そうだ that means "I hear" follows the plain form and has no そうな or そうに.

• × 降るそうな天気 → 降りそうな天気

そうな before a noun

With an adjective, そうな describes how the thing looks. With a verb, it describes something that looks about to happen.

おいしそうなけえきケーキ is a cake you have not tasted yet; おいしいけえきケーキ is one you know is good.

そうに before a verb

そうに describes how someone looks while doing something. It is the usual way to describe how someone else feels, since a feeling word like かなしい悲しい on its own speaks for the speaker.

そうになる

A verb's ます-stem with そうになる says something nearly happened: "almost".