What metaphors are used in The Hairy Ape by Eugene O'Neill?

Hell, in this play and in O'Neill's intent, is firstly and metaphorically imprisonment in the steel bars of the Upper Class's definitions of the role of the Working Class; but secondly, and more immediately, hell is man's animalistic, raw, unrestrained impulsive nature … a second hell which, in the mind and writing of Eugene O'Neill, leads to the first.