Increasing your click through rate in the SERPs or search engine results pages is one of the user metrics (see what are user metrics) which can have a very positive (or negative) influence on your ranking.
Think about it: Google and other major search engines want to serve their users the best possible experience, and that means rewarding via a better or more visible ranking the best content in all different ways. So how do they determine the different ways in which content is good? One of those ways comes from the click through rate in the SERPs, or how good your impression versus click rate is in the SERPs.
An "impression" is every time which a search engine results page which includes your web page is shown to a search engine user. So if you were ranking on the first page of Google for "pet care products" and someone searched for that phrase in Google to where your web page was appearing among the other listings on that search engine page, that would count as one impression. Obviously everyone isn't going to click on your listing every time it appears; they may click on another listing, on a paid listing, or if they don't find what they were looking for they may refine their search phrase or any number of other possibilities. That said, better your click through to impression rate is, the better you'll rank in the search engines because that says to the search engine that you have interesting content worth clicking through to.
So how to increase your click through rate in the SERPs?
Headline Headline Headline! - A good headline is the best thing you can do to get someone to click through to your page. And by headline I just mean the title of your page. Now as far as keyword research goes, check out my article on how to do keyword research correctly. Once you have your keyword picked out for that page, make sure to weave it naturally in your title. After that's been met, you can begin to look into creating a great title, which I've explained fully in this article on examples of great titles.
Meta Description - Your meta description is what appears in the SERPs below your title and is a close second in terms of importance of how to increase your click through rate in the SERPs. Not everyone clicks through based on the title of a page alone. Sometimes that can get their attention, but many people continue and read the description below to ensure that it's what they're looking for. Don't leave this up to chance by leaving it blank and letting the search engines take a random section of your text, write your own meta description describing the page and what someone will learn if they click through, and try to weave your keyword in here, as well.
Relevance - Lastly, make sure that everything is relevant to the search term. Generally if you're even showing up in the SERPs for a keyword phrase, then it's likely that your content is relevant to the phrase, but the point is to ensure that you're writing about relevant things as they relate to your site. So if you have a automotive themed website and URL, don't be trying to rank for puppy care related themes on your site because they will discourage people from clicking through, thus having a negative effect on your ranking.
Use those three tips to boost your click through rate in the SERPs and get more traffic + conversions sooner than later, even if you're already ranking well!