What's the most important secret to becoming a successful chef? Knowing the right ingredients to use. I think this is also the secret to becoming a successful investor.

The primary ingredients of investing are capital, time, and solid investment assets. How much money you can make depends on how much money you have to invest, how much time you have, and which assets you invest in.

Exchange-traded funds (ETFs) rank among the best investment assets for long-term investors. And Vanguard offers some of the most attractive ETFs around. Here are three Vanguard ETFs that can turn $500 per month into over $1 million.

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1. Vanguard S&P 500 ETF

I think the easiest choice to amass a $1 million fortune is the Vanguard S&P 500 ETF (VOO 0.39%). As its name indicates, this ETF aims to track the performance of the S&P 500 (^GSPC 0.40%), which includes the 500 largest U.S. companies.

Over the long run, the S&P 500 has delivered an average annual total return (with dividends reinvested) of around 10%. If you invested $500 per month and achieved that return, you'd have nearly $1.09 million at the end of 30 years. At the end of 40 years, your portfolio would be worth more than $2.9 million. These amounts, by the way, assume that you invest in a tax-advantaged account, such as an individual retirement account (IRA), and don't pull any money out along the way.

Granted, the Vanguard S&P 500 ETF hasn't been around for 30 or 40 years. Vanguard launched the fund in September 2010. Since its inception, the ETF has delivered an average annual total return of 13.6%. If you were able to make this higher return, your $500 per month would grow to over $1 million in only 24 years. After 30 years, you'd amass a fortune of over $2.2 million.

There's no guarantee that the Vanguard S&P 500 ETF will generate an average return of 13.6% -- or even 10%. However, those returns are certainly possible. One of the advantages of the S&P 500 is that it regularly replaces laggards with rising stars. It's also weighted by market cap, which means the stocks that grow the most affect the index's performance the most.

2. Vanguard S&P 500 Growth ETF

If the S&P 500 can achieve 10% returns over the long term, it stands to reason that the fastest-growing stocks in the index could deliver even greater returns. That's the premise behind the Vanguard S&P 500 Growth ETF (VOOG 0.52%).

This Vanguard ETF focuses only on growth stocks in the S&P 500. It currently owns 212 stocks, instead of the 505 stocks in the Vanguard S&P 500 ETF (this number is greater than 500 because some companies have multiple classes of shares).

Since its inception in September 2010, the Vanguard S&P 500 Growth ETF has generated an average annual return of 16.4%. If you were able to obtain this return and invested $500 per month, your money would grow to a little over $4 million in 30 years. You'd have $1 million within 22 years.

Can the Vanguard S&P 500 Growth ETF continue to deliver such a lofty return over the next several decades? Probably not. However, I think this fund could nonetheless turn $500 per month into over $1 million for those who begin investing at an early age.

3. Vanguard Russell 1000 Growth ETF

Let's expand our horizons somewhat. What if, instead of limiting ourselves to the growth stocks in the S&P 500, we invested in growth stocks in an index that held more stocks? The Vanguard Russell 1000 Growth ETF (VONG 0.43%) could be just the ticket.

This ETF attempts to track the performance of growth stocks in the Russell 1000 index. Whereas the S&P 500 owns shares of the 500 largest U.S. companies, the Russell 1000 owns shares of the largest 1,000 companies. The Vanguard Russell 1000 Growth ETF's portfolio currently includes 387 stocks.

Like the other two ETFs on our list, this Vanguard ETF began trading in September 2010. Since its inception, the fund has generated an average annual return of 16.9%. That makes it the best-performing ETF in the Vanguard family.

How long would it take to make $1 million investing $500 per month at that return? Less than 21 years. If you kept socking away money for 30 years, you'd have nearly $4.5 million.

Again, there's no way to know for sure whether the Vanguard Russell 1000 Growth ETF will provide such a sky-high return over the long term. I wouldn't count on it. But this Vanguard ETF could still provide a great vehicle for investors to make $1 million or more for retirement.