META Tags are relied on by search engines to help understand the content on your site. META tags do not display on your site, but are intertwined specifically with the page in question. It’s important to keep your keywords specific and concise, keeping in mind the content that is actually on the page. Google will penalise your site in rankings if your META tags and description are not in line with the actual content displayed. It’s worth using Google’s ‘Keyword Planner’ in Adwords, to help you plan your META Tags, content and description. The Keyword Planner will display the search volumes for the keywords in question, it would be ideal to use keywords that draw more search traffic, but remember the competition will also be more fierce.
See the following link for another useful tool to help you select keywords, http://keywordtool.io/.