Pattern-Lock is one of graphical authentication schemes that shows high popularity today. Based on recent research, the security requirements metrics of Pattern-Lock applications have not proposed yet. The goal of this study is to define security requirements metrics for Pattern-Lock applications on mobile devices. Our study has identified 12 threat statements and 18 requirements statements by analyzing STRIDE (Spoofing the identity, Tampering, Repudiation, Information disclosure, Denial of service, Elevation of privilege) and Extended Misuse Case diagram. To develop the metrics we have used Goal-Question-Metric (GQM) paradigm. Based on these, we develop 3 Goals and 7 Questions and resulted in 20 metrics for security requirements. The metrics have been evaluated using 30 App Locker Android applications, and the results show that some metrics have higher values than others. Number of Pattern Characteristics that Successfully Detected, Ability to Relock, and Grid Size metrics have the three highest values. These metrics requires higher priorities to look into when developers need to build the App Locker applications. Moreover, developers should ensure that App Locker applications have values higher than average of security goals and metrics achievements.