I've tried reading articles in Japanese on the multiple meanings なり has in Classical Japanese, but some articles seem to have more information than others and some just seem not too reliable.
To this point I know that when attached to a noun なり can act like a affirmative copula (as in 愛しき人なり=愛しい人である), having the meanings of である and にある. Apparently, though, when attached to verbs it can have the meanings of ようだ, as in ほととぎすはるかに今ぞ鳴くなる=ほととぎすは今はるかに鳴いているのを聞こえるよ・聞こえるようだ.
This is all, however, very confusing in my head, and I would appreciate if someone could give me a general overview on all the meanings なり has in Classical Japanese, both when it is attached to nouns and to verbs.