While the proven Zacks Rank places an emphasis on earnings estimates and estimate revisions to find strong stocks, we also know that investors tend to develop their own individual strategies. With this in mind, we are always looking at value, growth, and momentum trends to discover great companies.Looking at the history of these trends, perhaps none is more beloved than value investing. This strategy simply looks to identify companies that are being undervalued by the broader market. Value investors use a variety of methods, including tried-and-true valuation metrics, to find these stocks.On top of the Zacks Rank, investors can also look at our innovative Style Scores system to find stocks with specific traits. For example, value investors will want to focus on the "Value" category. Stocks with high Zacks Ranks and "A" grades for Value will be some of the highest-quality value stocks on the market today.One stock to keep an eye on is United Natural Foods (UNFI). UNFI is currently sporting a Zacks Rank of #1 (Strong Buy), as well as a Value grade of A. The stock holds a P/E ratio of 9.93, while its industry has an average P/E of 19.04. Over the last 12 months, UNFI's Forward P/E has been as high as 16.96 and as low as 4.28, with a median of 6.27.Investors should also recognize that UNFI has a P/B ratio of 0.81. The P/B ratio pits a stock's market value against 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 2.20. UNFI's P/B has been as high as 1.04 and as low as 0.23, with a median of 0.38, over the past year.These are only a few of the key metrics included in United Natural Foods'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, UNFI 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 United Natural Foods, Inc. (UNFI): Free Stock Analysis Report To read this article on Zacks.com click here.