Warren Buffett is not concerned by downward moves in the stock market.

Buffett is probably the most famous investor in the world. The Oracle of Omaha has amassed wealth estimated at $81.5 billion. He took Berkshire from a failing New England textile mill to an international conglomerate with a market cap of around $499 billion as of Oct. 2018.

The Dow Jones Industrial Average is now down for the year as rising material costs and tariffs put pressure on company profit margins, and there's also the fear of rising interest rates. While many investors are scared off by the market volatility, value investors should use the opportunity to consider stocks that are trading at a substantial discount.

Wells Fargo & Co.

Wells Fargo & Co. (NYSE: WFC) is the second largest holding in Buffett's portfolio, according to his 13F filing for the second quarter of 2018. He owns over 452 million shares at a market value of $25 billion as of that date. This holding is $4.5 billion larger than Kraft Heinz, his third-largest holding. Buffett first invested in the stock in 1989 and has grown his position since then. 

Wells Fargo is a bank with a number of different lines of business. The stock is trading around $51 as of Oct. 2018, well off its high of $66 in January. The company pays a dividend yield of 3.4%.

Buffett likes the company because it was able to weather the 2008 financial storm successfully. He also believes in the company's management. The financial ratios for the company are further impressive, as it has been able to grow its earnings per share at an impressive rate. Investors may want to follow Buffett and take a look at the stock while it is at a low price.

Axalta Coating Systems Ltd.

Axalta Coating Systems Ltd. (NYSE: AXTA) is a relatively new addition to Buffett's portfolio. Buffett opened a position buying 20 million shares in the second quarter of 2015. Buffett now owns 24.3 million shares after buying nearly 1 million shares in the second quarter of 2018.  

The company sells exterior coatings for automobiles. The Carlyle Group, a prominent private equity firm, bought the company from DuPont in 2013. Axalta had its initial public offering (IPO) in November 2014.

Berkshire bought the shares directly from DuPont for $28 a share. Shares hit an all-time high of $38 in late 2017, but are now trading at $24 a share. Buffett likes to target companies in the automotive sector. The fact that he bought almost a million shares last quarter while company shares were falling shows his commitment to Axalta. He owns almost 10% of the company.

Walmart Inc.

Walmart Inc. (NYSE: WMT) is another notable holding in Buffett's portfolio. The low-cost retailer lost significant value during 2015 but has since seen a noted turnaround. The stock has been making new all-time highs. The company pays a dividend yield of 2.1%. Buffett holds 1.39 million shares with a market value of $119 million as of the second quarter of 2018.

Buffett slowly built his position in the company but recently started dumping it. However, there is a silver lining. Buffett sold most of his stake in 2016, and since then shares have been on a tear. Buffett slowed the selloff of his shares and has since been playing wait-and-see. He could be looking to re-enter the position in size. 

Walmart grew its net revenues to $500 billion in 2017 from $486 billion in 2016. Although the retailer has encountered some difficulties recently, revenues are still strong, and the stock price is on the turnaround.