The different genres and divisions in the narrative allow the Metamorphoses to display a wide range of themes. Scholar Stephen M. Wheeler notes that "Metamorphosis, mutability, love, violence, artistry, and power are just some of the unifying themes that critics have proposed over the years." 
|“||In nova fert animus mutatas dicere formas / corpora;||”|
—Ov., Met., Book I, lines 1–2.
Metamorphosis or transformation is a unifying theme amongst the episodes of the Metamorphoses. Ovid raises its significance explicitly in the opening lines of the poem: In nova fert animus mutatas dicere formas / corpora; ("I intend to speak of forms changed into new entities;"). Accompanying this theme is often violence, inflicted upon a victim whose transformation becomes part of the natural landscape. This theme amalgamates the much-explored opposition between the hunter and the hunted and the thematic tension between art and nature.
There is a huge variety among the types of transformations that take place: from human to inanimate object (Nileus), constellation (Ariadne's Crown), animal (Perdix); from animal (Ants) and fungus (Mushrooms) to human; of sex (Hyenas); and of colour (Pebbles). The metamorphoses themselves are often located metatextually within the poem, through grammatical or narratorial transformations. At other times, transformations are developed into humour or absurdity, such that, slowly, “the reader realizes he is being had”, or the very nature of transformation is questioned or subverted. This phenomenon is merely one aspect of Ovid's extensive use of illusion and disguise.