What is the voltage across the circuit shown
Therefore there should be no voltage across the resistor, and resistor
  should act as open. Therefore VM2 should be zero.


An open circuit can have any voltage across with zero current through.  However, a resistor can only have zero volts across with zero current through so your reasoning is flawed.

But, this is actually a very common reasoning error among those learning electrical circuits.  To develop correct intuition, you must check it against the most fundamental circuit laws.

First, there's KVL.  We can write a KVL equation around the rightmost loop:

$$V_{R1} = V_{AM1} + V_{R5} + V_{M2}$$

This must hold.  If your intuition violates KVL, your intuition is leading you astray.

Second, we have Ohm's Law:

$$V_{R5} = 0A \cdot 100\Omega = 0V$$

Also, \$V_{AM1} = 0V\$ since it is an ideal ammeter.

Thus, regardless of your intuition, it must be the case that

$$V_{R1} = V_{M2}$$

The voltmeter reads the voltage across the resistor R1.

To help develop your intuition, think about moving the "top" voltmeter lead to the leftmost terminal of R5.  I think it is clear that the voltmeter will read the voltage across R1.

Now, since there is zero volts across R5, the voltage reading on either side of R5 must be the same.  In other words, moving the voltmeter lead back to the rightmost terminal of R5 should not change the voltmeter reading at all.