I always see Prince Phillip from Disney's Sleeping Beauty when I read this verse, though he is given a shield and not a helmet.
But what wonderful imagery! We're gearing up for a spiritual battle, the previous verses have spoke about other pieces of armor - the breastplate of righteousness, to protect your heart, the belt of truth to hold you together, you're feet fitted with readiness, the shield of faith.
And now the helmet of salvation.
So often our heads lead our hearts. We will know in our heart we are saved, but so many intellectual arguments against Jesus and his love hit us every day, that sometimes the biggest battle is to win over our heads.
How amazing to know God gives us a HELMET of salvation - we can KNOW by reading His word we are saved. And His word? What is it? Why, its the sword of the Spirit!
We will wage many battles as followers of Christ, be prepared, be ready, and keep God's word with you, it is your sword, it is your weapon against those that will tell you that Christ is a lie, that there is no God.
God has given us what we need to fight this battle. We just have to take it.
As a little postscript - if you're fighting an intellectual battle about God, there are a million resources out there - including the series "Faith without blindfolds" my husband taught for the Easter season. You can listen to them here.