Manjeet, I believe we already created a plugin for this. Please contact me if you want to hear more details.

@Manjeet if you are looking for paid support, We have developed this metatags plugin as part of seo works on elgg. You  can see a demo at

http://webgalli.com/pg/groups/1331/elgg-jquery-delete-plugin/

http://webgalli.com/pg/file/webgalli/read/2603/xmass-theme-for-elgg-with-snow-falling-effect

Just go through the source of these links and you can see that the metatags are different for each pages.

You can call me at +919496336479, (We are from Kerala, S.India)

(I have  already answered a duplicate post of this on another thread)

While adding new blog-posts, groups, etc. there is a field for tags.

@manjeet : by default, Elgg have the option to save tags to differnt entities. you can use these tags as metatags for your entities. I think, there is a metatags plugin available here in the community. Search for it.