Meta Tags , are they neccssary?

Yes they matter. Though they don't carry a ton of weight, they do help the search engine determine what the page is about. The most important thing is to make sure the meta-description is unique on every page, if it is not unique, you could drive right into the supplemental results in Google. The meta-keywords tag isn't all that important, I don't bother to put it on my pages, I just use meta-description. There are plenty of examples of website achieving a top 3 ranking in Google without meta tags, but they're good to have regardless.

To add to what Matt said, it's best to have a unique meta description. This helps the search engine to know what your page is about and to know that it's not duplicate content. If you can't have a unique meta description (i.e. if your CMS doesn't have that functionality), it's better to have no meta description.

Sometimes the SE will use the meta description as the description text in the SERPs. This is a good way to customize what users see and encourage them to click your result and not someone else's.

Don't Drop the Meta-Tags

"Several years ago the search engines devalued the use of meta-tags in determining rankings. But because they use the meta-tags as page descriptions in their SERP pages, you must make special efforts to ensure that the content presented to searchers inspires them to click on your links rather than your competitors'."

If you don't put meta-tags on your website's pages, then Yahoo and MSN (with a combined market share of around 45%) will just guess at what to put in the description of your website. They will pull phrases out of context (much the way Google does) from your site and slap them in there. The result is not nearly as inviting as it could have been otherwise. That's why it is always beneficial to learn to write effective meta-tags...

Even if they are using meta tags to place your site in a topical neighbourhood I still wouldn't say they are "necessary." They are not used directly in rankings in any of the major search engines to my knowledge. They are easy enough to put in on static pages - in that case, it's not taking much effort and it's certainly a good idea to include them. However, many content management systems don't include functionality to add custom meta tags for every page. Is it necssary to install that functionality or switch to another CMS just to get custom meta tags? Ehhh... there are worse things your CMS could be doing in regards to SEO. If it's not too much work to add them, then by all means do it! If it is, then it's probably okay to leave them out and focus on other aspects of SEO.

Elena mentioned a title meta tag - I am not aware a meta title tag, unless she's referring to the tag which is a different matter altogehter. Unique tags for every page are very necessary for many reasons!

the is the most important

yes it is important . specially title and description. it is good for search engine and visitors. so better to spend time on page optimization also.

Meta tags have been long part of on-page optimization. It does not carry the same weight as before in determining your rankings but still have relevance. So for more efficient SEO purposes, meta tags are still useful