Considering that Bakemonogatari largely centers around Araragi's connection to various women/girls who have varying levels of interest in him it wouldn't be entirely wrong to argue it's a harem
That is basically why I consider it a Harem.
If he wasn't pretty much "THE man" it would instantly negate that aspect... As well if he wasn't "The way in which all the other characters are fulfilled" it would also escape that.
I'm not sure where "metaphors" comes into it. Surrealism, maybe
Well it is simple... Take one of the character's curses... and imagine it as a metaphor for something that happens in real life.
Then watch the anime play out that metaphor.
Its like Buffy in that respect, but more non-sense.
And it's not a "psycho-girls" anime ala Mirai Nikki or anything.
Well then it advertises itself as unattractively as possible to me, and people describe it terribly to me.
"Ohh no I am weightless... I know I'll start carrying school supplies like a freeken psycho"
Me: "Why don't you... just... I don't know... buy body weights? They are a thing that exists"
"But then I won't be able to show myself undressing with sharp pointy objects poking out... Also are you honestly suggesting I wear something that will make me look LESS sexy?"
Me: "Dang what was I thinking? I'd make sarcastic remarks like a swimsuit episode or something... but I have a feeling there is one"
I am sorry but it is hard for me to get into an anime that advertises itself by showing me someone undressing. You are basically asking me to not only not judge a book by its cover, but also by the little blurb on the back, and everyone elses description.
By the by I consider Higurashi to also fall under "Psycho-girls". Any anime in which the point is that these female characters act off and nearly psychopathic.