Life does manifest in energy.
But you have to go with what you know. It is troublesome enough to come up with a definition of what life is. But of course you could come up with a definition that makes rocks come alive, only it wouldn't be very useful. Would seem like animism on a cosmic scale what you are proposing.
While you are right that we might have trouble recognizing life on different planets, because of all kinds of Earth-specific adaptations and environment impact-feedback loops and so on, there is reason for some optimism that we might recognize it and that it might at a certain basic level be actually quite similar to us.
There is a reason why we are made of the stuff we are made of, and that is that the stuff we're made of is quite common. And that it happens to have the right chemical (valence, polarities, bonding energies) properties. Not is this stuff abundantly present only on planet Earth but to be expected on other planets to a very far, but maximum distance as well. (This is when stars reach a certain level of "metallicity" - meaning they are younger stars that consist of more heavier elements like carbon, nitrogen, oxygen and so on. So there is an age limit at which (planetary) chemistry becomes sufficiently complex.)
The mechanisms involved in (bio-)chemical evolution that would give rise to basic metabolic mechanisms and even the base-pairs that form the basis of the entire genetic coding system (and consequential the possibilities for active - catalytic - metabolic systems of reactions and feedback loops forming autonomic systems) are not actually Earth-specific, they exist in interstellar space and can be synthesized under cryogenic circumstances. Even R/DNA might have a very humble and simple beginning in the abundance of polycyclic aromatic hydrocarbons on primordial Earth as they are elsewhere in the Universe.
All things unforeseen could happen, lots of surprises here on Earth of life adapting to the most inhospitable places imaginable and beyond, but when alien-hunting you have to go with what you know.
However as a counter note let's not get carried away, not that i expect a guy who doesnt believe in god to believe there might be aliens that are like super man.... my point is the other disturbing thing is people expecting aliens to look awry or have some form of power be it teleportation and what not from their type of evolution.
I'd say maybe even you might be amazed to find a more benign form of survival for the fittest let's say plant forms secrete this that other's eat and so on that predation and so forth isnt there. I might sound impying other world need be better but my implication is they can be anything, the question is why a monster or the next thing to superman.
p/s i read an article which i will post the link once i refind it of other possible lifeforms not similar to ours
i dont take aliens too seriously, not that i am a skeptic of them but the chance we will ever meet in this century, anyway i am more amazed by multiverse theory