Meta tags, do they all have a use?

I'm interesting to know, are all these various meta tags actually required for search engines? Do they make a significant difference to the position of your site or should we just leave them out?

The tags below were generated by an online meta tag tool. I wasn't aware some of them even existed, I have only been using, the title/keywords and content tags which I consider the 3 most important. Am I wrong in thinking that?

<META HTTP-EQUIV="Content-Language" CONTENT="EN">
<META NAME="distribution" CONTENT="Global">
<META HTTP-EQUIV="Expires" CONTENT="Tue, 07 Jun 2005 18:45:32 GMT">
<META NAME="revisit-after" CONTENT="">
<META NAME="robots" CONTENT="FOLLOW,INDEX">