Effective methods for metrics definition are of particular importance, as measurement mechanisms are indispensable in virtually any engineering discipline. The paper describes how the well known Goal-Question-Metric (GQM) method of systematic metrics derivation from measurement goals can be extended by applying argument structures. The proposed approach is called Goal-Argument-Metric (GAM). The general ideas of GQM and GAM are briefly introduced and they are followed by the comparison of the two approaches. Next, the Trust-IT framework is described – it is used to develop argument structures in GAM. Then a case study of application of GAM is presented. The case study concerns derivation of metrics and direct measurements with the objective to assess effectiveness of Standards Conformity Framework (SCF), which is currently under development. In conclusion, early experience with GAM is presented and more information about on-going research on argument structures is given.