A student writes “implicit metaphor” for “By the dawn when it breathes” and stops. The label points in a plausible direction but does not identify the implied comparator or the sign that supports it.
A complete answer explains that dawn is represented as an animate being; the being itself is unspoken, while breathing is ascribed to dawn, making the gradual emergence of morning vivid.
The rule: a classification needs textual evidence and an explanation of effect.