This whitepaper is an article that covers the basic structure of Metasploit and the need for it as a framework. It provides guidance on the different techniques of information gathering and scans.
You can download it from the following link: https://packetstormsecurity.com/files/download/103600/Metasploit_KarthikR.pdf
Source: https://packetstormsecurity.com/files/103600/Sneak-Peak-At-The-Metasploit-Framework.html