As per my experience keywords density is the trick where from we can use 3% density in the article body. Google consider density and provide preference for the keywords to get top ranking in the search engine. This task included in the On-page optimization to set-up content structure.

Shawn Swail

In my own experience, the keyword density is important (2%-3% is good); but it is more important that whether your keywords added (H1, H2 tags; Meta description; anchor text...)