This isn’t my article but I had to repost it because its so good.  It explains why using meta keywords is becoming obsolete and why focus keywords are the way forwards.

It’s a completely new way of thinking for most of my clients, because we have been brainwashed into thinking that we have to stuff our keywords into a box and BOOM! our customers will find us.  We need to be smarter than that and this article tells you why….

https://yoast.com/focus-keyword/