Many fledged studies suggest that conceptual metaphor has three basic functions. They are guiding perceptions, structuralizing experience, creating new insight, which will be discussed one by one briefly.
Firstly, conceptual metaphor guides people to perceive experiences and knowledge about the world. According to the previous analysis above, conceptual metaphor greatly influences people’s thinking and largely shapes the conceptual system of people without being noticed, due to which it can guide the ways people perceive the outside world. For example, conceptual metaphor such as UP IS GOOD, DOWN IS BAD are deeply rooted in people’s mind, thus they usually express their emotions or feelings by saying “I’m feeling up”, “He looks down”, “She has high spirits”, etc. In a word, conceptual metaphor plays an indispensable role in dominating the way of people’s thinking, namely guiding perceptions.
Secondly, besides helping perceiving the world, conceptual metaphor also contributes to structuralizing knowledge about the ambiguous and abstract targets via the familiar and simple sources that people can experience directly. Take conceptual metaphor LOVE IS JOURNEY as an example, people may organize knowledge of love by mapping the personal experience of a journey onto the former one. Then some knowledge of the abstract concept love is shown to people. To sum up, it is conceptual metaphor that serves as a tool for people structuralizing the experience of the targets.
 
Last but not the least, conceptual metaphor not only builds similarities between the targets and the sources, but also gives new meanings to the previous and the current concepts, thus offering people novel ways of understanding and experience the world. In short, it provides people with different perspectives of understanding some concepts. This phenomenon often shows obviously in cross-cultural situations, where people with different cultural backgrounds hold distinct sources domain of one same target. During communications, fresh ideas about an old concept will be formed and people’s conceptual system will be perfect.

2.3.3.2 Discourse Functions Of Conceptual Metaphor
In discourse analysis, there are two important devices called cohesion and coherence. According to Halliday and Hasan, cohesion is pided into five types, reference, substitution, conjunction, ellipsis and lexical cohesion. Coherence refers to a kind of relationship that connects two meanings of utterances in a discourse. And this connection may be based on the communicators' shared knowledge and mutual context. It is generally believed that cohesion can promote coherence and metaphor can interpret cohesion and reinforce the coherence of discourse.

2.3.3.2.1 Cohesive Functions
In a discourse, conceptual metaphor creates cohesion by utilizing various cohesive devices. According to Halliday and Hasan, there are three main cohesive devices: reference, reiteration and collocation.

It has been proved that only endophoric? reference can make cohesion. And endophoric reference includes personal, demonstrative and comparative reference. Personal reference means the use of personals, such as “his”, “her”, “he”, “she”, “it”, “their”, etc. Similarly, demonstrative reference is reference that depends on location. When the thing is close to the speaker, he can use “this”, “these”, “here”, etc. While it is far, he can use “that”, “those”, or “there”. Differently, comparative reference is an indirect reference, which has two types. One is general comparison and another one is particular comparison. General comparison only involves likeness and unlikeness while particular comparison touches upon the concept of quality and quantity by exerting “better”, “more”, “fewer” and so on. In short, each of the three references contributes to cohesion in a discourse in different ways. 美剧《复仇》的语篇分析(5):http://www.youerw.com/yingyu/lunwen_9177.html