It is important to remember that all of Neruda's poems were written in Spanish, and therefore what we see are translations of those poems into English. Obviously, meter is impacted by translation, so clearly the answer I will give you is based on the translation of the poem, rather than the original.
Having given this caveat, if we look at the poem, it is clear that there is no regular meter. Consider the following stanza, for example:
With a chaste heart
With pure eyes I celebrate your beauty
Holding the leash of blood
So that it might leap out and trace your outline
Where you lie down in my Ode
As in a land of forests or in surf
In aromatic loam, or in sea music
We can see that such free verse lacks the regularity of a definite meter that gives it structure. There are of course instances in particular lines when an iambic meter is loosely used, such as "In aromatic loam, or in sea music," but the stanza as a whole contains a number of variations so we can definitively state that a regular meter is not used in this poem. Perhaps we can relate this to Neruda's style: he did not want what he was describing to be "boxed in" through strict meter and rhyme, and it allows him to express his philosophical thoughts and emotions about what he witnesses with ease and flexibility.