Abstract: Metaphor processing and understanding (MPU) has been a focus of studies in question and has experienced a long history of evolution, which could be traced back to the works of Aristotle who started the tradition of implicit comparison in MPU. Followers conducted studies under such frameworks as the pure matching theory, salience imbalance theory, and domain-interaction theories. There is no dying that significant achievements had been being made ever since, yet the divergence of views in this research field is what helps move forward studies on MPU. A remarkable trend is studies conducted under a new research paradigm, the concept construction of MPU. The present article offered explanations from three research theories: theory of lexical pragmatics, theory of Recanati's, and theory of class-inclusion. It is believed that MPU involves both the use of previously acquired concepts and the creation of new ones, the ad hoc concepts. The ad hoc concept results from concept broadening and concept narrowing, a general pragmatic process of concept adjustment. Explanations from the three research models have offered important insights into metaphor processing and understanding.