The speaker describes a closet that is always open yet hides everything inside it. The closet is clearly a metaphor for the self: the "skeletons and bones" and "dirty little secrets" suggest things the speaker is ashamed of or afraid to reveal. The title's "closet" may also hint at the idea of "coming out," though the poem never says so directly, so that reading is only a possibility.
The speaker feels fear and isolation. The closet is dark because the speaker is "scared of what you'll find," and it is too small to share, which suggests there is no room for other people. Yet there is a quiet hope too: the secrets stay hidden "until someone I can trust" stumbles on them. The final stanza adds a monster that seems huge only until someone shouts, hinting that the fear may be less powerful than the speaker believes. The mood is anxious, guarded, and lonely, with a small flicker of longing to be understood.