Is Keywords Meta Tag Relevant?
Meta Tags is being used to order search engines like Google, Bing ect. how to index your website's pages and it's content. These Meta Tags are embedded on the HEAD part of the pages codes and invisible to the visitors of you website. The are appear on the results of search on the search engines as a Title and Description.
While Page Title, Description Meta Tags and other meta tags have high importance for indexing on search engines, the Keywords Meta Tag has lost it's importance on September 2009, when search engines like Google and others stopped using it for indexing websites. The main reason for that was the bad use of this Meta Tag by overflowing it with many keywords and specially overflowing it with irrelevent keywords. This bad use caused the search engines to show irrelevant and wrong results.
For example, SEOs and webmasters were adding keywords that not appeared on the contect of the page at all or using names of competitors on this tag.
Therefore, if you adding Meta Tags to your pages, there's no need in the Keywords Meta Tag at all. If you decide to add this meta tag anyway, search engines will ignore it and it won't carry any weight on your website's ranking.
It is more important to care about your Page Title and Description Meta Tag and it's relevance to the pages content.