The keyword meta tag is oldschool and was used on every page decades ago. It has been massively abused by spammers who stuffed all kind of keywords into it. Today it’s outdated. Google decided 2010 to completely drop it as a ranking factor. Yahoo indexes the meta keyword but it’s handled as the lowest ranking signal.
Bing says: “Getting it right is a nice perk for us, but won’t rock your world. Abusing meta keywords can hurt you”.
<meta name="keywords" content="seo, search engine optimization">
Should I use meta keywords?
Better save your time and do not use it. If you carefully put relevant keywords into it your site may be seen as overoptimized and it may get a penalty. The 3 big searchengines do not give real value to it. Chances are higher for a negative impact than improvings.
Your competitor could also easily spy on your targeted exact keyword.