Young investors who are saving for retirement need to focus on capital growth, and exchange-traded funds (ETFs) are great tools to deliver that. However, not every ETF is suitable for growth-oriented investors, so it's important to identify those that are primed to maximize upside opportunity over the long term. These make wonderful additions to IRAs, especially Roth IRAs, which allow you to cash out in retirement without paying capital gains tax.

Investors who hold the below ETFs will have an opportunity to beat the market over the long term, but they'll need to pay high valuations and endure extra volatility along the way. Make sure you are comfortable with those drawbacks before prioritizing growth above all else.

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General growth

Vanguard is a trusted institution with a reputation that was gained by minimizing expenses and popularizing index investing. Its popular family of funds includes the Vanguard Growth ETF (NYSEMKT:VUG), which is the largest growth-specific ETF available.

The Vanguard Growth ETF holds large-cap and mid-cap stocks, which are selected based on a group of metrics that indicate above-average growth rates. The fund's portfolio of 270 holdings provides diversification without taking on slow-moving, mature giants that would prevent returns from beating the market. Investors will love the ultra-thin 0.04% expense ratio, meaning the fund manager doesn't shave off a sizable chunk of your investment each year. Shares are also very liquid with $200 million in daily trading volume and a 0.02% average bid-ask spread. It won't be expensive or inefficient to buy and sell the ETF.

Investors should note that this fund is heavily concentrated in the consumer cyclical and tech sectors, which represent 75% of its total holdings. That's pretty common among growth-oriented portfolios, but it still warrants consideration.

Robotics and AI

Automation and analytics will be an important part of every sector of the economy in the future. The companies that develop the associated robots and software are likely to deliver exceptional growth, and the Global X Robotics & Artificial Intelligence ETF (NASDAQ:BOTZ) is designed specifically to invest in those stocks.

The ETF holds 32 stocks from developed countries that create robotics and AI software. These technologies have a number of applications, including drones, healthcare, and analytics software.

The fund is the largest of its niche with $2.4 billion in assets under management. Investors will appreciate the fund's liquidity with narrow spreads and high daily trading volume. However, it is expensive to own. At 0.68%, this expense ratio creates a substantial bar to overcome each year. Still, the promise of focused hyper-growth is enough to convince bullish investors that the ETF is worth the price of admission.

Blockchain

Cryptocurrencies have risen to prominence among both speculators and growth investors. Regardless of your stance on these digital assets or your predictions for individual tokens, blockchain technology has been a revolutionary development. Distributed ledgers are likely to reshape financial systems, legal contracts, asset ownership, and countless other aspects of sharable data.

The Amplify Transformational Data Sharing ETF (NYSEMKT:BLOK) is an actively-managed vehicle that currently holds around 50 different stocks that develop or monetize blockchain technology. While its focus is fairly niche, it is diversified within that space -- no stock is more than 5.5% of the whole portfolio.

The active management strategy results in a high 0.70% expense ratio, and it carries large trading expenses now due to relatively low volume. If you are looking for diverse exposure to the tech fueling the crypto revolution, without actually getting involved with digital currency, then consider this ETF.

Cybersecurity

As we become more deeply connected through digital networks, protecting ourselves from the associated risks becomes more important. That was apparent for businesses last year as employees were forced to share sensitive information while working remotely. Swelling numbers of e-commerce buyers also want to see their payment information protected. Telehealth companies have a massive regulatory burden to protect patient data. Ransomware attacks, like the one that shut down the Colonial Pipeline, can completely derail business operations.

Companies that develop and administer security software will experience continued demand for their services. The ETFMG Prime Cyber Security ETF (NYSEMKT:HACK) allows you to own the whole industry, rather than picking a winner. It holds 58 stocks offering security hardware, software, or services.

The ETFMG Cyber Security fund deploys an equal-weighting methodology to keep it from being overexposed to the largest companies in the space. That's good news for growth investors who don't mind a little extra risk. The 0.60% expense ratio is once again a bit high, but investors are hoping this sector can outpace the major indexes by a substantial margin over the long term.

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.