A metaphor is defined as an indirect comparison between two or more seemingly unrelated subjects that typically uses “is a” to join the subjects.
The formula of metaphor:
A metaphor casts a first subject (tenor) as being equal to a second subject (vehicle) in some way. Thus, the first subject can be economically described thanks to the implicit and explicit attributes of the second.
There are many classifications of metaphors, but the classification which you gave us the most simple and clear. Semantically there are: - genuine, which possess extreme degre of unexpectedness, according to Galperin; For example when I think of love, i want to say love is a perfume, because we fill it from a distance and for a long time if it's trully and vice versa it quickly erode if not real. - trite, often appear in texts and are sometimes fixed in dictionaries. Ex.: life is a journey.
Structurally there are: - simple, which consist of one word or word-group. Ex.: I'll crew on it! (crew - think) - prolonged, in which one word, used in a metaphorical sence. - mixed, which begin with one comparison, but change to another illogically.