It's hard to believe there are still more than five months left in 2020, because Wall Street and investors have already experienced about a decade's worth of volatility crammed into the past couple of months.

The coronavirus disease 2019 (COVID-19) pandemic has done quite the number on the stock market. In less than a five-week stretch during the first quarter, the broad-based S&P 500 lost a whopping 34% of its value. Then, during the second quarter, the S&P 500 turned in its best performance in 22 years. No one has a clue what to expect next, and it clearly shows with the CBOE Volatility Index remaining well above its historic average.

But if there's good news to be had here, it's that periods of panic and volatility have always represented a buying opportunity for long-term investors. Every single stock market correction in the S&P 500 (save for the existing correction) has eventually been put into the rearview mirror by a bull market rally. That bodes well for patient investors who choose to invest their money into game-changing businesses.

Five one hundred dollar bills neatly laid out.

Image source: Getty Images.

Maybe the best aspect of investing in stocks is that you don't need to have a fortune to make one. If you have $500 in disposable cash that won't be needed for bills or emergencies, you have more than enough capital to start investing in great stocks. Here are a trio of great companies to consider buying right now.

Bristol Myers Squibb

Though all the rage at the moment is over COVID-19 vaccine developers, I'd much prefer investing in a tried-and-true Big Pharma like Bristol Myers Squibb (NYSE:BMY).

One of the most exciting developments for the company was the completion of its Celgene acquisition in November 2019. Buying Celgene brought an assortment of cancer and immunology therapies into the fold, none of which is more important than Revlimid. Multiple myeloma drug Revlimid has seen increased demand, longer duration of use, and Celgene never had any issue raising the price of its lead drug on a nearly annual basis. Best of all, Revlimid's label continues to expand, and it's protected from a full flood of generic competition until the end of January 2026. It's going to be a cash cow for Bristol Myers for years to come.

Beyond Revlimid, Bristol Myers has two blockbuster drugs that have been absolute stars. There's the leading oral anticoagulant Eliquis, which was co-developed with Pfizer, and cancer immunotherapy Opdivo, which looks to be on its way to roughly $7 billion in 2020 sales. Opdivo has dozens of ongoing clinical studies that may well result in label expansion opportunities. In my view, it should grow into a $10 billion a year therapy. 

With steady mid-single-digit organic sales growth and a forward price-to-earnings ratio of around 8, Bristol Myers Squibb is ripe for the picking.

A person inserting their Cash Card into a Square point-of-sale card reader.

Image source: Square.

Square

Another smart way to invest $500 right now would be to buy a disruptor in the financial technology space like Square (NYSE:SQ). Though it's had one heck of a run of late, Square has all the potential to be a 10-bagger over the next decade.

To be clear, Square's seller ecosystem, which is what the company is best-known for, was already seeing plenty of growth prior to COVID-19. In 2019, the company had a little over $106 billion in payments cross its point-of-sale platform, demonstrating that it is, slowly but surely, disrupting the old-school use of cash and clawing away processing share from the traditional players like Visa and Mastercard. However, COVID-19 has consumers leery of using cash, which has only accelerated this transition toward cashless transactions.

Perhaps the most exciting trend for Square's seller ecosystem is that it's witnessed a steady uptick in usage from larger businesses -- a large business is defined by Square as having more than $125,000 in annualized gross payment volume (GPV). In the first quarter, 52% of GPV originated with these larger merchants, which suggests that Square isn't just a platform used by small-and-medium-sized businesses any longer.

And no discussion of Square is complete without mentioning Cash App. This peer-to-peer financial platform finds itself in the right place at the right time. Having more than tripled its monthly active user count, Square reported record enrollments in March and April. Cash App's ability to transfer to and from traditional bank accounts, as well as be linked to Cash Card and used as a debit card, should allow Cash App to become Square's leading profit driver within two years.

According to Wall Street, Square's sales are set to more than quadruple by 2023, which is more than enough reason to buy into this growth story.

An engineer placing a hard drive into a server tower.

Image source: Getty Images.

Western Digital

A final great stock to invest $500 into right now is data storage solutions specialist Western Digital (NASDAQ:WDC).

An initial look at Western Digital might scare some people off. The company suspended its dividend in the latest quarter, and its share price has been more than halved since the beginning of 2018. As a highly cyclical business, storage is prone to disruption and commoditization during periods of economic contraction or recession. But this shouldn't scare off prospective investors. Rather, it's giving opportunistic investors a chance to buy a storage kingpin at an exceptional discount.

Over the very near-term, Western Digital expects to benefit from the release of next-generation gaming consoles. These new consoles require beefed up storage capacity, which COO Michael D. Cordano believes is a "multi-exabyte opportunity this calendar year." It's possible that COVID-19 might delay or stagger the launch of these new consoles, but there'll nevertheless be a steady uptick in revenue as a result of gaming innovation.

But gaming consoles aren't why investors should be excited about Western Digital. The real growth story here is all about data center storage solutions. We were already seeing businesses move into remote workspaces and utilize shared clouds long before COVID-19 made its presence known. But with the pandemic here to stay (for now), it's encouraging businesses to spare no cost to digitize their data and build accessible cloud platforms. That's a resounding endorsement for a storage solutions provider like Western Digital.

With the company's dividend suspended, it now has close to $600 million extra each year to pay down its debt and reinvest in storage solutions that'll be tailored to data centers and cloud-focused businesses. That makes Western Digital a stock that long-term investors should want to own.