The first item of the armor is the belt of truth. Why a belt? I mean a belt is the LAST thing you put on when you get dressed, right? Who puts on a belt first? What is God thinking here? I am not sure, but I think I have an idea. Follow along with me if you will.
First let's look at truth, in the original language it is aletheia. Aletheia signifying "the reality lying at the basis of an appearance; the manifested, veritable essence of a matter" and "not merely verbal, but sincerity and integrity of character".

We don't like the truth anymore, about ourselves, about others, about sin. We don't like it at all, we'd rather skirt around the truth, we gloss over the truth, we find the truth harsh and unwavering.
So we are told in Ephesians to begin with the Truth. That in itself is a tall order my friends. Something that going forward, I will endeavor to do. If I find that I can't, I will just be quiet. Nothing of good substance and honor can begin with less. Relationships, stories, business deals - they all have to begin with the truth. If we don't we have built our house upon the sand instead of the bedrock of truth.
It is of note that in the Old Testament the majority of times the English word truth appears it refers to our mouths. It is often paired with righteousness and refers to justice. In the New Testament most references are to THE truth. In the book of John, he refers to the Spirit of Truth which is the Holy Spirit.
For me, it's a lot less difficult to start out with the truth if I recognize that it is God's Truth where we begin. Knowing how fallable we are, HE gives us something to hold fast to and that is the Spirit of Truth.
May you be greatly blessed today and thank you for reading!