I learned basis of assembly language with, both, AT&T and Intel style. After that I gone through buffer overflow and how to use shellcode with it. Should I go for Metasploit now?
Metasploit can generate some malicious files, such as PDFs. Malware analysis isn't necessarily just Windows PE files so it might be a good idea to look into other file formats. Metaploit could be useful to generate your own samples to analyze.
Msfvenom might be interesting to you as well. It is a tool that generates shellcode given a payload. Generated shellcode might not always be the best though.