Design patterns are gaining popularity because they support modifiability and flexibility of designs. Design patterns are solutions to frequently recurring problems in design. Reverse engineering of source code primarily focuses on the software architecture. Understanding software architecture in terms of design patterns simplifies the process of identifying some key properties such as coupling, flexibility and maintainability. This paper presents a novel approach to extract design patterns using structural metrics of object-oriented programs. It involves two steps. In the first step, structural metrics are extracted from the source code. In the second step, these metrics are matched with the properties of structural design patterns of Gang-of-Four to identify a design pattern. Our approach is demonstrated by extracting design patterns from a Java program using our pattern extraction tool.