The fifth piece of armor All Christians have mentioned in Ephesians 6:17 is "the helment of Salvation." For the protection of your soul which consists in (the hope of) salvation.

The term “helmet” is derived from a compound Greek term conveying the idea of “around the head.” The imagery appears to be borrowed from Isaiah 59:17, where it is applied to Jehovah, a divine warrior. The power of God to defeat his enemies and save his people.

The helmet of salvation has inscribed in it the the words Holy to the Lord, the Same Words That Were Inscribed on the Golden Crown of the High Priest.

Salvation Comes the Lord Who is your Deliverer!

sōtēría – salvation, i.e. God's rescue which delivers believers out of destruction and into His safety, properly, deliver out of danger and into safety; used principally of God rescuing believers from the penalty and power of sin – and into His provisions (safety).

The helmet of salvation is more than knowing you are saved, it is knowing who you are and what was done for you and What you now posesses as the born again child of God. It goes beyond the moment of salvation, to encompass the full scope and expression of salvation past, present and future.

The Helment if Salvation preserves you in the day of spiritual conflict, and will guard you from the blows which an enemy would strike.

The primary battlefield of spiritual warfare is at the threshold of the mind, where thoughts compete with one another. God knew you would need to have a strong spiritual defense. So He armed you with the Helmet of Salvation.

The enemy tries to wear down your defenses and corrupt your way of thinking with subtle reasonings, false teachings, anything to confuse and distract your mind from God's best for you. And the Good Works He purposed and plan to do through you. (Ephesians 2:10)

God knew that tactics the enemy would use against you, so when you were born again; Christ came to live in you. It is no longer you who lives, but Christ lives in you. (Galatians 2:20)

Now by the action of His power that is at work within you, you are able to carry out His purpose and do. superabundantly, far over and above all that you dare ask or think, infinitely beyond our highest prayers, desires, thoughts, hopes, or dreams.–(Ephesians ‭3:20‬)

So when you put on the helmet of salvation, it is a reminder that you have the mind of Christ (the Messiah) and do hold the thoughts (feelings and purposes) of His heart. (Isaiah 40:13, 1 Corinthians ‭2:16)‬

Now, God having equipped you with His Thoughts, His Truth, His Wisdom, and His Revelation. You are Able to be strong in the Lord, being empowered through your union with Him; drawing your strength from Him, which His boundless might provides.

And having on God's whole armor which God supplies, you are be able successfully to stand up against all the strategies and the deceits of the devil. (Ephesians ‭6:10-11)‬ Empowered from on High by God to stand against Satan's Furious Attacks.

Therefore, the helmet of salvation is the Presence and the wisdom of God in you by virtue of you being in Christ Jesus and he being in you. Who enables you to do the right thing without hesitation. So you can respond to an unexpected situation, just as Christ would; then you have the mind of Christ.