Pun and metonym have a key position in several significant conceptions of literature due to their formative and critical functions to language and cognition. Both rhetorical tropes share some common characteristics regarding their constructions and functions. This paper illustrates the relation between pun and metonymy considering their cognitive functions, constructions and working mechanism as it seems to be no research on English pun and their relation to metonymy have been conducted to date. Therefore, a comprehensive analysis will be made regarding these significant language phenomena by exploring some examples (24 samples) which will be analyzed for demonstrating that the usage of puns leads to the occurrence of metonymy. Analytical descriptive method will be followed.