Here at Zacks, our focus is on the proven Zacks Rank system, which emphasizes earnings estimates and estimate revisions to find great stocks. Nevertheless, we are always paying attention to the latest value, growth, and momentum trends to underscore strong picks.Of these, value investing is easily one of the most popular ways to find great stocks in any market environment. Value investors use a variety of methods, including tried-and-true valuation metrics, to find these stocks.Luckily, Zacks has developed its own Style Scores system in an effort to find stocks with specific traits. Value investors will be interested in the system's "Value" category. Stocks with both "A" grades in the Value category and high Zacks Ranks are among the strongest value stocks on the market right now.One stock to keep an eye on is Contura Energy (CTRA). CTRA is currently sporting a Zacks Rank of #1 (Strong Buy), as well as an A grade for Value.Investors should also recognize that CTRA has a P/B ratio of 0.32. The P/B is a method of comparing a stock's market value to its book value, which is defined as total assets minus total liabilities. This company's current P/B looks solid when compared to its industry's average P/B of 0.48. Over the past year, CTRA's P/B has been as high as 0.51 and as low as 0.05, with a median of 0.16.Value investors also love the P/S ratio, which is calculated by simply dividing a stock's price with the company's sales. Some people prefer this metric because sales are harder to manipulate on an income statement. This means it could be a truer performance indicator. CTRA has a P/S ratio of 0.07. This compares to its industry's average P/S of 0.2.These are only a few of the key metrics included in Contura Energy's strong Value grade, but they help show that the stock is likely undervalued right now. When factoring in the strength of its earnings outlook, CTRA looks like an impressive value stock at the moment.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Contura Energy, Inc. (CTRA): Free Stock Analysis Report To read this article on Zacks.com click here.