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.

Of these, perhaps no stock market trend is more popular than value investing, which is a strategy that has proven to be successful in all sorts of market environments. Value investors use a variety of methods, including tried-and-true valuation metrics, to find these stocks.

Zacks has developed the innovative Style Scores system to highlight stocks with specific traits. For example, value investors will be interested in stocks with great grades in the "Value" category. When paired with a high Zacks Rank, "A" grades in the Value category are among the strongest value stocks on the market today.

One company value investors might notice is Amkor Technology (AMKR Quick QuoteAMKR - Free Report) . AMKR is currently holding a Zacks Rank of #1 (Strong Buy) and a Value grade of A. The stock holds a P/E ratio of 15.20, while its industry has an average P/E of 32.36. AMKR's Forward P/E has been as high as 23.94 and as low as 8.56, with a median of 14.90, all within the past year.

Value investors also use the P/S ratio. The P/S ratio is is calculated as price divided by sales. This is a prefered metric because revenue can't really be manipulated, so sales are often a truer performance indicator. AMKR has a P/S ratio of 1.28. This compares to its industry's average P/S of 3.83.

Value investors will likely look at more than just these metrics, but the above data helps show that Amkor Technology is likely undervalued currently. And when considering the strength of its earnings outlook, AMKR sticks out at as one of the market's strongest value stocks.