Theophilus,
Grammatically and exegetically Peter is the rock. Catholic apologist, James Akin, rightly argues: "In Matthew 16:17-19, Jesus makes three statements. All three begin with an assertion concerning Peter. Each assertion is then followed by a two-part elaboration consisting of a contrast (human/divine revelation, Christ’s/Satan’s activity, heavenly ratification of earthly binding/loosing). This elaboration develops the meaning of the principal assertion.
The exegetical structure of Matthew 16:17-19
Statement/Assertion 1
17 "Blessed are you, Simon Bar-Jona!
Elaboration # ! For flesh and blood has not revealed this to you,
Elaboration # 2 but my Father who is in heaven.
Statement/Assertion 2
18 And I tell you, you are Peter,
Elaboration #1 and on this rock I will build my church,
Elaboration # 2 and the gates of hell shall not prevail against it.
Statement/Assertion 3
19 I will give you the keys of the kingdom of heaven,
Elaboration #1 and whatever you bind on earth shall be bound in heaven,
Elaboration # 2 and whatever you loose on earth shall be loosed in heaven."
The exegetical structure of the passage demands that Peter be the rock:
Statements 1 and 3 have Peter as their principal subject, therefore statement 2 does as well.
Statements 1 and 3 are blessings on Peter, therefore statement 2 is as well. The elaborations in statements 1 and 3 develop the meaning of the assertions in those statements, therefore the elaborations in statement 2 develop the meaning of statement 2.
Faced with these facts, as well as others … I was forced to conclude that Peter is, indeed the rock that Jesus was speaking of. Many Evangelical exegetes admit the same thing. However, they immediately try to block any implications being drawn from this fact. They try to shut down the chain of inference and isolate the datum so that it cannot give rise to any ecclesiological inferences."
I hope this explanation by Akin helps.