Metasploit Framework is the best penetration tool, it has 3 different version. The Metasploit Community Edition (free and web-based user interface for Metasploit), Metasploit Express (an open-core commercial edition for security teams who need to verify vulnerabilities), and Metasploit Pro ( an open-core commercial Metasploit edition for penetration testers). Now how to mastering Metasploit Framework?
Metasploit Unleashed is the answer. Metasploit Unleashed is free online version of the course. It explain how to use Metasploit Framework from zero become hero. There are basic, introduction of Metasploit Framework, reference, and etc.
So if you want to be a master Metasploit Framework, check this site out!