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 rely on traditional forms of analysis on key valuation metrics to find stocks that they believe are undervalued, leaving room for profits.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 company value investors might notice is Alcoa (AA). AA is currently sporting a Zacks Rank of #2 (Buy), as well as a Value grade of A.Another notable valuation metric for AA is its P/B ratio of 0.93. 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 stock's P/B looks solid versus its industry's average P/B of 1.20. AA's P/B has been as high as 0.93 and as low as 0.17, with a median of 0.46, over the past year.Value investors also frequently use the P/S ratio. This metric is found by dividing a stock's price with the company's revenue. This is a popular metric because sales are harder to manipulate on an income statement, so they are often considered a better performance indicator. AA has a P/S ratio of 0.46. This compares to its industry's average P/S of 0.56.These are just a handful of the figures considered in Alcoa's great Value grade. Still, they help show that the stock is likely being undervalued at the moment. Add this to the strength of its earnings outlook, and we can clearly see that AA is an impressive value stock right now.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 Alcoa Corp. (AA): Free Stock Analysis Report To read this article on Zacks.com click here.