We have multiple adages that have the same underlying message. "Look before you leap." "Haste makes waste." "Measure twice, cut once." The idea behind all of them is that you should think things through before doing something.

That's great advice for investors. However, some stocks don't require nearly as much analysis as others. And a few are practically no-brainers. Here are three monster stocks to buy without any hesitation.

1. Amazon

Amazon (AMZN -1.51%) isn't an 800-pound gorilla in e-commerce -- it's a 900-pound gorilla. The company accounts for nearly 38% of the U.S. e-commerce market, according to Statista. Market researcher PYMTS puts the number at 48%. The market share for Amazon's closest rival -- Walmart -- is no higher than 7% using either data source.

It's a closer contest in cloud services, but Amazon still reigns as king of that fast-growing market. Amazon Web Services ranks as the top cloud infrastructure provider with a market share of 32%. That's well ahead of No. 2 Microsoft Azure's market share of 22%.

The great news for investors is that Amazon has plenty of room to grow in both e-commerce and cloud services. E-commerce only made up 15.6% of total U.S. retail sales in the third quarter. Amazon continues to expand its online footprint by moving into new areas such as selling cars. Currently, less than 10% of global IT spending is in the cloud. That percentage is expected to skyrocket over the next 10 to 15 years.

In the meantime, Amazon is focused on increasing its profits like never before. The company's earnings more than tripled year over year in Q3. With this type of improvement combined with the opportunities presented by generative AI, Amazon should keep up its winning ways for a long time to come.

2. MercadoLibre

Amazon doesn't dominate e-commerce everywhere. In Latin America, MercadoLibre (MELI -0.58%) rules. That's especially the case in Brazil, where the company enjoys a market share of more than 50%.

Business is booming for MercadoLibre. Its net revenue soared 69% year over year in Q3 on a constant-currency basis. Gross merchandise volume jumped 59%. The number of unique buyers grew by 18% year over year.

E-commerce isn't MercadoLibre's only business, though. The company's logistics unit achieved a record fulfillment penetration of 48% in Q3. Its fintech digital account total payment volume vaulted nearly 189% higher on a constant-currency basis.

Latin America's e-commerce volume is much smaller than the markets in North America, Europe, and Asia. However, that gives MercadoLibre strong growth opportunities. The company also has great prospects in Latin America's fintech market.

3. Vertex Pharmaceuticals

An estimated 88,000 people in the U.S., Europe, Australia, and Canada have cystic fibrosis. Only four therapies are approved for treating the underlying cause of the rare genetic disease. Vertex Pharmaceuticals (VRTX -1.86%) makes all of them.

Despite having a monopoly in cystic fibrosis, Vertex still has room for growth in the market. It's securing additional approvals and reimbursement deals to treat younger patients. The company is also developing new therapies for the condition. Vertex expects to soon report results from late-stage studies of its vanzacaftor triple-drug combo, which could be its most powerful cystic fibrosis therapy yet. And it's working with Moderna on developing a messenger RNA drug that could help the roughly 5,000 patients who can't benefit from current therapies.

Vertex isn't stopping at cystic fibrosis, though. The big biotech recently won U.S. approval for exa-cel as a treatment for sickle cell disease. It hopes to pick up a second U.S. approval for the gene-editing therapy as a treatment for transfusion-dependent beta-thalassemia in the first quarter of 2024.

In addition, Vertex's pipeline is loaded with promising programs. VX-548 holds the potential to become a blockbuster non-opioid pain treatment. Inaxaplin could become the first approved therapy that treats the underlying cause of APOL1-mediated kidney disease, which affects more patients than cystic fibrosis. Vertex also is moving forward with several candidates that could effectively cure type 1 diabetes. With this abundance of riches in its pipeline, this stock -- like Amazon and MercadoLibre -- is a monster that should grow even bigger.