I often hear sentences in movies like "Fight back, you coward!", "You filthy, dirty hippy", etc. And I had thought it sounded like this only to me but when I found the subtitles for those movies, I made sure there's really not "to be" verb after "you". Can I delete "are" word in that case in informal language if I learn AmE? P.S. I think I gotta say that my friend from UK said he didn't ever hear same thing in the speaking of his mates. And all movies when I've noticed the absence of "are" are American, British-American or Canadian.
The lack of a verb-to-be between “you” and “coward” is normal in the given context. Coward serves as an appositive to you.
Apposition is a grammatical construction in which two elements, normally noun phrases, are placed side by side, with one element serving to identify the other in a different way; the two elements are said to be in apposition. - Wikipedia
The Wikipedia article provides this example, among others:
He likes the television showP The SimpsonsA.
– There are many television shows, and he likes that particular one.
The word coward provides information about the word you in your example.
OK, this could get a little complicated. In English, the conjunction “are” is not used before a noun (coward, in your example) WITHOUT the one letter word “a” following it. Ex....
“You are a coward.”
However, it doesn’t read or speak fluidly to say, “Fight back, you are a coward” because “You are a coward” is its own sentence.
One could write, “Fight back! You are cowardly!” (using it as an adverb, but that sounds like a poor English translation of a subtitled martial arts movie).
Bottom line, for your writing to sound correct in American English, leave “are” out of it. When it’s a direct me-accusing-you statement, there should be no word before “coward” except perhaps another adjective, such as “yellow bellied.”