This study carries out Systemic Functional Linguistic (Halliday and Matthiessen, 2014) and Critical Discourse (Fairclough, 1995; van Dijk 1993) Analyses of a corpus of tweets posted by the former American president Barack Obama, the 44th President of the United States (@POTUS44), while in office. The data is processed using a Corpus Linguistic tool called UAM CorpusTool (O'Donnell, 2008) to facilitate the process of generating quantitative results. This study focuses on how Obama, as an American president, utilizes social media tools, with focus on his presidential Twitter account. This study also aims at investigating how the president intends to maintain relations and exploit this type of discourse to exercise power over his audience (followers). Systemic Functional Grammar is utilized in this study to examine the verbal representations according to the functions each tweet performs. This framework is capable of analyzing texts in terms of: a) how relationships are maintained between the speakers and their audiences (interpersonal metafunction); b) how speakers express themselves (ideational metafunction); and c) how they organize such expressions and feelings in their texts in spoken/written form (textual metafunction). This study concludes that tweets posted by presidents, specifically Obama, tackle different topics: education, international affairs, society, healthcare, etc.