Instead of something frightening, the "monsters" here are the childlike, tender parts of ourselves. The speaker imagines them wanting what most of us want: to be loved and cherished, to receive letters, to enjoy the extra calories on a favourite cake, to scream happily on a roller coaster. The monsters are drawn to small, quiet pleasures too, like lying on an open terrace watching the stars, or dancing like raindrops to a song. They even light up at being handed some old childhood junk, which suggests they hold on to sentimental things.
The repeated line "Our monsters within" works like a gentle refrain, bringing us back to the same affectionate idea each time. The closing line, "are as easy as pie," is short and playful. It says these inner selves are simple to please. The mood is warm, nostalgic and lightly humorous, with a quiet reminder that joy often comes from small, ordinary things. The poem's wording is a little uneven in places, but its kindness toward our hidden selves comes through clearly.