The answer depends on the fine print of the semantic story.
One common line makes it come out that a wff with free variables counts as true-in-$\mathcal{M}$ just when its universal closure comes out true.
But alternatively you can have it that a wff with free variables gets no true-value with respect to $\mathcal{M}\ $ -- it only gets a value with respect to $\mathcal{M} + \mathcal{I}$ where $\mathcal{I}$ is an assignment function mapping variables to elements of $\mathcal{M}$'s domain (in effect giving the variables an interpretation as temporary names).
In some ways, the second story is more natural: the first conforms with informal mathematical practice of treating sentences with free variables as implicitly universally quantified. But you can go either way.