The devil is constantly busy! Don’t take that lightly! Consider it again: The devil is constantly busy! The use of the Greek present tense verbs in 1 Peter 5:8 emphasizes this truth. The Greek present tense indicates continuous, ongoing action in the present. Therefore, we learn that the devil “is walking about” — constant activity (NASB has “prowls”). He is a “roaring lion” — roaring is a verb in Greek (not an adjective), emphasizing an ongoing behavior. He is “seeking someone” — 
continuously in search of targets. The verse then switches to a different tense (aorist) on the last verb to emphasize a settled, resulting condition — “someone to devour.” The “devouring” is not pictured (in this verse) as a continuous activity, but as a one-time-and-it’s-over event (like an animal devouring its prey).
With a view of our adversary’s constant endeavors, God tells us to do three things: (1) Be sober (self-controlled); (2) Be watchful (on the alert); (3) Resist him (firm in your faith)!