Importing exploits in to Metasploit (Kali 2.0)

Good day fellas,

So, after searching for almost 2 days with mostly outdated tutorials I learned how to use external exploits.

But, now the problem is that I am only able to work with .rb exploits, why? Anything other than that would just not show up in the metasploit. like .py. Can anyone show me the way around it?

Don't you think it will leave me with very limited number of options if only .rb exploits work.