Keyword Meta tags are no longer used by Google for web search ranking!
That being said, keywords are still the backbone for SEO. As long as content remains to be the King, keywords and keyword phrases are truly valuable, since they are capable of driving in traffic to a website. Keyword research helps in identifying niche terms to focus on while writing content for your web pages.
Most of the time new websites will need to compete with existing, well established websites in their industry. Merely targeting highly competitive keywords would take a whole lot of time to get the website to show up in SERPs. Keyword research would help identify less competitive keywords that can easily be targeted and results attained. This would help start small and grow gradually.
Google Analytics can also be used to identify the various keywords that were used by visitors to land on any webpage on your site. We can very well get to see new keyword combinations that were used to land on your web pages, and give more insight on the topics that users are interested in.
Here is my preferred keyword search tool: https://adwords.google.com/select/KeywordToolExternal