Heat the butter in a large skillet over medium-high heat until melted and shimmering.
Add the minced garlic to the skillet and sauté for about 30-60 seconds until fragrant. Be careful not to burn the garlic.
Add the frozen green beans directly to the skillet. Stir to coat them with the garlic butter.
Cook, stirring occasionally, for about 5-7 minutes, or until the green beans are heated through and tender-crisp. You want them to retain a slight bite.
Season with salt and black pepper to taste. If using, add a pinch of red pepper flakes.
Stir everything together well. For an extra burst of freshness, add a small squeeze of lemon juice just before serving.
Serve immediately as a delicious side dish.