can you say, "Toi cam thay rat met moi"??? Because I sure do! (The question is can rat go somewhere besides right after the subject, which is the only place I've seen it so far.)
Yes! Very tired
according to some native speakers, "mệt mỏi" is a much more formal word, and actually has a sense of being mentally tired. to say that you're physically tired it's much more common to just use "mệt"