Definition for poetry:​

Literary work in which special intensity is given to the expression of feelings and ideas by the use of distinctive style and rhythm; poems collectively or as a genre of literature.

it ends with a marriage, but also with prospero giving up his power.

the tempest is a play written by william shakespeare between 1610-1611, it narrates the story of prospero a magician that sets a storm to wreck a ship, this sets the story to kill the king of naples. while it is a romantic style play, it isn´t traditional because of the ending, it end with the marriage and the magician giving up his powers.