Fresh thyme can be used more generously than dried as it is not as concentrated.
In a large skillet with a tight-fitting lid, bring 1/2 inch water to a boil; salt generously.
Add green beans; reduce to a simmer, and cover skillet. Steam beans, tossing occasionally, until crisp-tender, 6 to 10 minutes.
Pull lid back slightly, and tilt skillet to drain water from green beans; add lemon juice, butter, and thyme. Season with salt and pepper, and toss to melt butter. Serve green beans garnished with additional thyme, if desired.