The Armor of God - The Shield Of Faith

The next piece of armor for the Roman soldier is the largest and therefore covers most of his surface area. In defence the soldier will use the shield to fend off all arrows, projectiles as well as the sword and so it had to work for him.
Ephesians 6:16
New King James Version (NKJV)
¹⁶ above all, taking the shield of faith with which you will be able to quench all the fiery darts of the wicked one.
For the shield to be effective, it had to be made of a strong material and yet be light. Now we need to remember that this shield was part of the Roman soldier's armory in the first century and not the twentieth century and so we have to rule out aluminum alloy or stainless steel. So say that the shield was cut out of wood but then the soldier will be lugging along a weighty burden.
Now I submit to you that the shield was actually made out of cow-hide (or bull-hide) because the Roman soldier loves his meat and there are plenty in those countries they conquered. Cow-hide will be lighter than wood and to make it pliable, they soak their shields in water and because the hide is soaking wet, any fiery arrows (darts as in the NKJV above) will be quenched when they are lodged in the shield.
We also note that the shield actually stretched from the soldiers eye down to his toes and the Romans invented the concept of the military tank; they had the ability to form a box with those on the inside holding their shields above their heads thus enclosing themselves from fiery arrows from above their heads in addition to all the sides.
Why did Paul use the shield for his instruction on faith? I submit to you that the weapon the devil uses against us is accusations and lies about our positions of righteousness. He needs to  get us disoriented first so that when we lower our guard he will then attack us directly.
1 Peter 5:8-9
New King James Version (NKJV)
⁸ Be sober, be vigilant; because^[a] your adversary the devil walks about like a roaring lion, seeking whom he may devour. ⁹ Resist him, steadfast in the faith, knowing that the same sufferings are experienced by your brotherhood in the world.

Peter tells us that the devil walks around like a roaring lion seeking whom he may devour. Notice a lion only roars when he wants to intimidate its prey. Once he is stalking its prey, he will switch to silent mode so that its prey does not know what hit it; a complete surprise. Notice Peter also mentions our weapon against the devil - our faith.

So my friend, continue to exercise your faith every day to build our spiritual strength and when the devil realizes that we are not in the category of 'devourable' he will have no choice but to leave us alone.