This technical note describes the main features of Metrix, a software that computes metric field from a priori error estimates or meshes and that handles several metric operations. The aim of the software, the input and the output files, the list of modules and options are given in this document. References that explain the various possibilities of the code are provided. Metrix has been developed within the GAMMA research project at INRIA Paris-Rocquencourt. This document describes the features of the current version: release V1.2 (January 2009).