A straightforward statement such as “I am sad” reports a condition. An elaborated poetic scene, by contrast, may enact the emotional meaning through its total image.
The discussion notes that declarative wording can serve an expressive or non-informative purpose. A further distinction concerns whether the whole expression is transferred by resemblance to another situation or by some other relation.
The analytical question is whether the speaker is primarily presenting verifiable information or producing an emotional response through the utterance as a unit.