Metasploit isn't a vulnerability scanner, it's an exploit framework.
It features an array of pre-built and automated exploits for virtually point-and-click exploitation...
Can it crash servers? Likely. It is after all actively exploiting the vulnerability.

For example, one of its most usefull payload is the VNC server: that's right, find a machine with ms-rpc unpatched, point metasploit at it, select your payload, launch, poof, you've got a VNC window on the machine...


Ammo