If you conduct any sort of social media marketing, this metric will be important because you want to be aware of how Facebook, Instagram and other networks are returning your investment in their advertisement packages.
This is a ranking factor, but mostly it is an experience factor. If your website is slow, you should be looking at the changes you need to make to improve that, because although search engines will eventually penalize your site for lack of performance, your ultimate goal is still to attract and retain visitors, and visitors are known to be less patient than search engines.
Are visitors leaving as soon as they land? This is an important metric because if the person visiting your website leaves a few seconds later, that means your content needs to be revisited. Either the message is carrying little value, or it is being poorly presented.
Strong loyalty means higher search engine ranking.If your visitors are devoting enough time to study what you are offering search engines will interpret your website as a good supplier of valuable content. On the other hand, if your bounce rate is high, and your time on site is low, your website is likely to get penalized by search engines as it will be interpreted as a poor supplier of valuable content.
Search Traffic is a good indicator to keep an eye on because you can compare week over week or month over month, and it tells you if traffic is following a trend or if it has suffered a drastic decrease or increase. These results will dictate whether the website requires the attention of the webmaster or not.
Keep an eye on your conversions over time primarily trying to find where are they coming from, and if it is heading in the right direction. Again, make changes accordingly.