Metasploit is a popular open-source framework used for penetration testing and security research. It provides tools for finding and exploiting vulnerabilities in software and systems, helping security professionals assess the security of their networks. The framework includes a vast collection of exploits, payloads, and auxiliary modules, making it easier for users to simulate attacks. By using Metasploit, organizations can identify weaknesses before malicious hackers do, ultimately improving their overall cybersecurity posture.