Patient investors can reap great rewards. It's easy to get caught up in the market's gain. After all, the current bull market has created wealth for many equity investors. The S&P 500 index has returned more than 26% this year (through Nov. 14) alone.

But stocks can have volatile returns. For instance, 2022 was a challenging year that saw the market lose 18.1%. Those that sold missed out on subsequent gains.

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Hence, it's important to take a long-term view. Investing over a long period smooths out short-term volatility. One way to invest and grow your money is through the Vanguard S&P 500 ETF (NYSEMKT: VOO). In fact, it can make you a millionaire if you invest $300 monthly and hold your investment for 30 years.

Of course, this requires making an assumption about returns, but the point is that you'll see how your money can grow nicely if you have a long-term approach.

Low fees

The Vanguard S&P 500 ETF (NYSEMKT: VOO) charges a low annual expense fee. That's because the ETF invests passively in the S&P 500 index. It's a big advantage that allows the index to beat many actively managed funds.

It has a 0.03 expense ratio. That's lower than the average 0.77% expense ratio for similar funds.

Vanguard's S&P 500 ETF also has lower expenses than its rival SPDR S&P 500 ETF Trust (NYSEMKT: SPY), which has a 0.09% expense ratio.

Although not a great difference, it does add up over time. Why pay higher expenses for the same product? After all, lower expenses mean higher returns.

Index composition

Many news organizations talk about the S&P 500, but it's worth understanding how the index works. The S&P 500 index's holdings, and hence, the Vanguard ETF's, are weighted based on stocks' market capitalization. That is, more valuable companies have greater weight and influence on returns. While these change over time based on market performance, it's useful to know what stocks and sectors you're investing in.

The 10 largest stocks make up about 35% of the ETF as of Oct. 31. These include Apple (NASDAQ: AAPL), Nvidia (NASDAQ: NVDA), Microsoft (NASDAQ: MSFT), Amazon (NASDAQ: AMZN), and Meta Platforms (NASDAQ: META).

Information technology has the largest sector weighting, 31.7%. That's followed by financials' 13.3%, healthcare's 11.2%, consumer discretionary's 10%, and communication services' 9.1%.

The calculation

While it may prove challenging to pinpoint future returns, the past can guide you. The Vanguard S&P 500 ETF has returned 12.96% annually over the last 10 years through Oct. 31. That's nearly identical to the underlying index's 13%.