This essential offers a compact introduction to the theory of Fermi liquid for physics students in their main studies. It forms the basis for an understanding of theoretical solid state physics and is part of every introductory lecture on this topic. After a brief overview of the Sommerfeld model of metals, the concept of the quasiparticle is introduced. Important calculations characterizing a Fermi liquid are derived in detailed calculations. The essential concludes with an overview of the microscopic theory of Fermi liquids. This Springer essential is a translation of the original German 1st edition essentials, Theorie der Fermiflüssigkeit in Metallen by Michael Kinza, published by Springer Fachmedien Wiesbaden GmbH, part of Springer Nature in 2018. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation. Springer Nature works continuously to further the development of tools for the production of books and on the related technologies to support the authors.