Do you think I cannot call on my Father, and he will at once put at my disposal more than twelve legions of angels?
Jesus had just finished stating to His Father that He was surrendered to launching Himself into the jaws of death (Matthew 26:42). Why then would He say this, that He could beckon "legions of angels" to His aid? He said this because He knew who He was. There are times when our obedience to the Father's will may seem to come full against our identity. To Jesus, though, this was not a conflict. Rather, it was a challenge to Peter, and to His disciples within earshot: If I can submit to what I'm about to go through, so can you; it's time to put your sword away and step up to the true plan that is at stake.
After all, Jesus had given them the keys to the Kingdom. It was their time to take the reigns of advancing the it on earth.
Again, Jesus had surrendered to the Father's agenda - that He pay the price for our brokenness, our sin. Yet in the context of His arrest, He stated twice that this was happening to fulfill the scriptures (Matthew 26:54 and Matthew 26:56). Is He really then just sacrificing Himself to make sure the prophecies are accurate? No. From the very first words, "In the beginning" (Genesis 1:1). the scriptures are the Father's agenda - which is to love us to a place of reconciliation through His Son.
Jesus is the consummation of the Father's heart for every human soul. And only through Jesus is that consummation complete. In Matthew 26, we have now fully entered into a place in this gospel where we can no longer use the words and actions of Jesus as a touchpoint to reflect upon the application of Jesus' words and actions to ourselves. We are now in a place where we can only witness what Jesus is willingly going through and reflect with reverential gratitude on the massive act that is unfolding for us all.