A close example of perfect competition
Though perfect competition is a hypothetical economic model, commodity markets offer many of the defining characteristics of a perfectly competitive market.
Suppose you're buying wheat flour or corn at the grocery store. You probably don't care what company milled the wheat or grew the corn. The products are interchangeable to you and most customers; if one bag of wheat flour costs $0.25 less than the others, there's a good chance you'd choose it over the competition. Wheat flour isn't exactly a product that inspires a lot of brand loyalty.
Still, commodity markets lack some of the hallmark traits of a perfectly competitive market. For example, it's not exactly easy or cheap to set up a flour mill or plant a cornfield, nor is it simple to walk away from such a venture. Although the production processes may be similar, one company could still develop new technology to mill flour or grow corn more efficiently than its competitors or find a way to lower its transportation costs.
The concept of perfect competition provides a valuable framework for understanding how markets function. But in the real world, no pure example of perfect competition exists.