While it's not a full poem, it uses personification, a figure of speech where inanimate objects are given human qualities, to create a vivid image.
Here's why:
* Green grass: Grass is not a living being, it cannot dance.
* Danced: This action implies movement and intention, traits associated with living beings.
This phrase could be used as the opening line of a poem, setting the scene and tone for the rest of the piece.