In the first expression it is more of that "we stick together", or correctly, "you stick yourself on to me". The person who says it is possessive and self confident. It is not "space giving" in any way.
Your suggestion is quite right but I would rather say: "You are made for me." (like a piece in a jig-saw-puzzle.
Thanks for answering, Porfyhr, but I don't completely understand. Does it actually imply "made for" as opposed to "for"? Is there another sentence which would mean simply "You are for me"?
Let's leave "You are mine"
We all agree about that.
The requester have asked for "meaning only" and the first sentence is a bit more vague and as I wrote depending on the dialect. I you ar very far south, Oslo, or north like Bodø the expression will vary and if we go to Trondheim or Bergen we will have different small variations.
The meaning; that should be noticed is that you are on me, you stick to me, you are glued to me, you and I fit together but we aren't a pair, you aren't my type but we hang on although... etc.; is we aren't a pair
I am a bit tired but "you are on me" doesn't sound so english to me... what do you experts say?