The Meaning of the Word, 'Is'

When Christ instituted the Lord's Supper, He said 'This is My body.'  Apparently, Christians believe most everything else Christ said and did from their reading of the Bible, except for that one thing.  Sure, God created the heavens and the earth with His word.  His Word states that Christ was resurrected.  Christ promised He will return to receive His bride, His Church.  Christ's Word raised Lazarus from the grave.  Christ's Word healed others that He came across.  Yeah... those things, God the Father, the Son, and the Holy Spirit have done.  We believe those things, because God has proclaimed those things in the Bible.  The very book that Christians claim to be God-breathed and is inerrant.

Then why is it that the meaning of words change when it comes to this:

And when the hour came, he reclined at table, and the apostles with him. And he said to them, “I have earnestly desired to eat this Passover with you before I suffer. For I tell you I will not eat it until it is fulfilled in the kingdom of God.” And he took a cup, and when he had given thanks he said, “Take this, and divide it among yourselves. For I tell you that from now on I will not drink of the fruit of the vine until the kingdom of God comes.” And he took bread, and when he had given thanks, he broke it and gave it to them, saying, “This is my body, which is given for you. Do this in remembrance of me.” And likewise the cup after they had eaten, saying, “This cup that is poured out for you is the new covenant in my blood. But behold, the hand of him who betrays me is with me on the table. For the Son of Man goes as it has been determined, but woe to that man by whom he is betrayed!” And they began to question one another, which of them it could be who was going to do this.  (Luke 22:14-23 ESV - bold italics mine)

Apparently, Christ didn't mean that, and what He really said was 'This is not My body, but just a metaphor, a mere symbol!'

Why does Christ all of sudden go symbolic or metaphoric?  He doesn't.  Words have meaning.  We, as readers, don't change the meanings of words because they need to fit our rational minds.  'Is' does mean 'is.'  If we truly trust God and His Word, and that we trust Him that He will do a good work, for He is just and merciful and holy; then why not trust His entire counsel.  Trust His Word in totality.  He is a trustworthy God, and He is faithful and true.