For nearly 18 months, investors have enjoyed a historic rally. Since bottoming out on March 23, 2020, the benchmark S&P 500 has more than doubled in value. Considering that most bear market bounce-back rallies feature wild swings in both directions, this has truly been something special for patient investors.

But even with the market near an all-time high, bargains can still be found. The key is to find innovative businesses to hold onto for long periods of time. If you have $500 ready to invest, these are some of the smartest stocks you can buy right now.

Five neatly staggered one hundred dollar bills.

Image source: Getty Images.

Visa

Although the stock market offers no guarantees, history has shown time and again that any double-digit percentage pullback in payment-processing company Visa (NYSE:V) is an opportunity for investors to pounce.

One of the biggest reasons Visa is such a success story is the company's cyclical ties. This is to say that consumers and businesses spend more when the U.S. and global economy are firing on all cylinders. Even though recessions are an inevitable part of the economic cycle, they usually only last for a few months or a couple of quarters. By comparison, economic expansions can last for years, or even a decade. Thus, Visa enjoys a disproportionately long period in the sun, and its shareholders know it.

Visa is also incredibly dominant when it comes to market share. In the U.S., the largest market for consumption in the world, Visa controlled 53% of credit card network purchase volume in 2018. That was more than 30 percentage points higher than its next-closest competitor. Its share of the U.S. market also expanded more than any other payment processor since the end of the Great Recession.

If you want a long growth runway, Visa has that, too. A majority of the world's transactions are still conducted in cash, which means there's a multi-decade opportunity to shift these cash sales to plastic, or some other form of digital payment. Visa can use its cash flow to push into underbanked regions, or it could choose the inorganic route, such as in 2016, when it acquired Visa Europe.

Lastly, take notice that Visa acts solely as a payment processor and doesn't lend, like some of its peers. While Visa is, theoretically, leaving interest income and fee potential on the table by not lending, it's also protecting itself from those aforementioned inevitable recessions. When economic contractions strike and credit delinquencies rise, Visa doesn't have to set aside capital for potential losses. This is why it bounces back from downturns so quickly.

An up-close view of a gold bar.

Image source: Getty Images.

Kirkland Lake Gold

Another extremely smart stock investors can buy right now with $500 is gold miner Kirkland Lake Gold (NYSE:KL). That's because there are macroeconomic and company-specific reasons to believe Kirkland Lake is headed higher.

For starters, physical gold remains an attractive investment opportunity. Bonds and other forms of "safe" income are sporting yields near historic lows, and the Federal Reserve hasn't taken its foot off the gas when it comes to quantitative easing measures. To boot, inflation has been picking up in a big way. This combination of low bond yields and rapidly rising inflation is often a recipe that pushes investors to put some of their money to work in physical gold as a store of value. And if the product Kirkland Lake Gold mines and sells increases in value, that's a good thing.

On a more company-specific basis, Kirkland Lake offers some of the lowest-cost mines in the industry, and it boasts the best balance sheet of the bunch. Through the first six months of 2021, the company's all-in sustaining costs (AISC) came in at $810 per gold ounce. 

AISC is an all-in measure of what it takes to operate a mine, but it also includes corporate and administrative costs, as well as sustaining exploration costs and capital expenditures. At an AISC of $810, Kirkland Lake is netting roughly a $1,000 margin per gold ounce.

What's more, this gold stock's balance sheet is unsurpassed. It ended June with $858.4 million in cash and no debt. While most gold stocks are still attempting to pay down debt following their frivolous spending in the early 2010s, Kirkland Lake has been able to repurchase 20 million shares of its common stock and triple its dividend since the beginning of last year. With almost $1.4 billion in operating cash flow over the trailing-12-month period, Kirkland Lake's capital returns should be among the best of the gold industry.

With Wall Street projecting $5 or more in annual free cash flow per share for Kirkland Lake through 2024, it looks like one lustrous bargain.

Person getting an injection.

Image source: Getty Images.

Novavax

A third and final smart stock begging to be bought with $500 is clinical-stage biotech company Novavax (NASDAQ:NVAX). Though I wouldn't usually refer to a clinical-stage biotech stock as a "smart buy," the likely approval of what should be Novavax's first blockbuster treatment makes it highly attractive for long-term investors.

Novavax's potential path to riches will likely come on the coattails of experimental coronavirus disease 2019 (COVID-19) vaccine NVX-CoV2373. In a large-scale study in the U.K., this vaccine produced a vaccine efficacy (VE) of 89.7%. Keep in mind this included total VE for the original COVID-19 virus and the U.K. variant. In June, a second large trial in the U.S. and Mexico yielded a similar VE of 90.4%.

Even though there's more to a vaccine than just initial efficacy, NVX-CoV2373 has a real shot to become the No. 3 COVID-19 vaccine in developed markets and push companies like Johnson & Johnson and AstraZeneca to the back of the line.

The reason such an amazing opportunity exists for investors is Novavax's multiple delays in filing for emergency use authorization (EUA). Though it's probably missed out on some low-hanging fruit, so to speak, the opportunity to be a difference-maker in developed markets and globally still remains. The company's U.S. EUA filing should be in the fourth quarter, with sales expected to skyrocket in the coming years.

Equally exciting is Novavax's early stage work on a combination COVID-19/influenza vaccine. While it's not the only company working on a combination vaccine -- Moderna recently announced it's working on a combo shot, too -- it does have the ability to beat most, if not all, of its competitors to market with a combination treatment. 

With Novavax, we could be witnessing the birth of a true innovator in the biotech space.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.