You've likely heard some form of the disclaimer, "Past performance is no guarantee of future results." And the statement is true. However, I'd add something to the disclaimer: "But a big head start is nearly always a good thing."

Several large-cap stocks have a big head start that could enable them to finish the year strong. I predict these will be the three best-performing S&P 500 (SNPINDEX: ^GSPC) stocks of 2024.

1. Nvidia

Nvidia (NASDAQ: NVDA) currently ranks as the biggest year-to-date winner in the S&P 500. Shares of the GPU maker have skyrocketed over 150%. I don't think Nvidia will give up its top spot by the end of 2024.

On Aug. 12, I predicted that Nvidia stock would jump another 20% or more by year-end. My prediction has almost come true already. One reason why is that some of the factors weighing on Nvidia aren't as worrisome now.

More importantly, though, Nvidia has yet to announce its fiscal 2025 second-quarter results. The company is scheduled to provide its Q2 update on Aug. 28. I fully expect another blow-out quarter for Nvidia, which will fuel investor optimism.

I also think the company will reassure investors about the timing of the launch of its Blackwell-based chips. Blackwell is Nvidia's newest GPU architecture that CEO Jensen Huang believes will be the most successful product in the company's history.

2. Super Micro Computer

Super Micro Computer (NASDAQ: SMCI), commonly referred to as Supermicro, ranks as the S&P 500's second-best stock so far this year. Shares of the information technology infrastructure company have soared around 115%. I expect Supermicro will add to that gain over the next few months.

Will Supermicro's upcoming 10-for-1 stock split on Oct. 1 provide a big catalyst? Maybe, but I wouldn't count on it. Even if there is a boost from the split, it could only be a temporary one.

The smarter reason to look for a continued strong performance from Supermicro is the tailwind generated by artificial intelligence (AI). In the fourth quarter of Supermicro's fiscal 2024, the company generated revenue of $5.31 billion. It projects revenue of between $6 billion and $7 billion in fiscal 2025 Q1. That's a 22% increase in just three months -- and much of it stems from AI-related demand.

Supermicro could also benefit from Nvidia's launch of its Blackwell chips. Even if there's a worse-than-expected delay with this launch, though, Supermicro CEO Charles Liang doesn't think his company will be affected too much because of the overall demand for its liquid-cooling solutions.

3. Eli Lilly

I'm going out on a limb with my next pick. Three S&P 500 stocks are currently performing better than Eli Lilly (NYSE: LLY) in addition to Nvidia and Supermicro. However, I have a hunch this big pharma stock could leap past them to end the year as the No. 3 stock in the S&P.

My bullish view about Lilly is based largely on my great expectations for the company's tirzepatide franchise. In the U.S., the drug is marketed under the brand name Mounjaro for treating type 2 diabetes and under the brand name Zepbound for treating obesity. Outside the U.S., it's marketed as Mounjaro for both indications. Whatever you call it, tirzepatide is already an enormously successful blockbuster drug. Mounjaro raked in $3.09 billion in sales in Q2, while Zepbound made $1.24 billion.

Investors also know that Lilly could have more indications for tirzepatide on the way. The U.S. Food and Drug Administration (FDA) could make an approval decision on the drug in treating obstructive sleep apnea and obesity by the end of 2024. Lilly plans to file for regulatory approvals of tirzepatide in treating heart failure with preserved ejection fraction (HFpEF) and obesity later this year.

We can't overlook Lilly's recently FDA-approved Alzheimer's disease drug, Kisunla. I don't look for jaw-dropping sales numbers from the therapy in the second half of the year. However, more regulatory approvals outside the U.S. are possible by the end of 2024. And if U.S. sales are better than expected, Kisunla could provide more reason for investors to be excited about Lilly's growth prospects.

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Keith Speights has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Nvidia. The Motley Fool has a disclosure policy.

Prediction: These Will Be the Best-Performing S&P 500 Stocks of 2024 was originally published by The Motley Fool