When used with the verb stem そう expresses that something is likely to happen or be true based on your own first-hand experience or judgment.
|It looks like it’s going to rain.|
Context: You’ve looked up at the sky and seen dark clouds.
|It seems like it’s going to take some time, eh?|
Context: You think the task is going to be difficult.
|He’s got a look that says he’s interested in her, right?|
Context: You’re sat across the table and your friend keeps looking at the girl.
|A likely reason.|
We can connect the phrase to noun using な and to a verb using に.
|To almost hit an oncoming car.|
It can also be used with the potential.
|Do you reckon you can do it? (Does it seem like you can do it?)|
To make the sentence negative we add にない.
|It doesn’t seem I can do it|
そう can also be used with adjectives. For i-adjectives we need to get rid of the final い; for na-adjective we append そう without the な particle.
|An expensive-looking apartment.|
Context: You don’t know the rent but you’ve seen the luxury furnishings inside.
|The cake looks delicious!|
|A convenient-sounding system.|
Context: You’ve not used the system yourself, but you’ve read the details and can imagine it’s convenient.