Impossible to say without a description of the planet and environment they inhabit. A creature from a very hot, wet world with gravity only one tenth as strong as that on Earth would, for example, look very different to one from cold, dry planet with gravity ten times stronger than that on Earth.

The more interesting question is what we look like to them. I always enjoyed that Star Trek: Next Generation episode where the crystalline life form's first comment through the Universal Translator was "Ugly. Very ugly bags of mostly water."

Transformers. I am hoping for transformers. ?

I think the first forms of extraterrestrial life we discover will resemble extremophiles in some way. Regardless, they will be fantastical life forms.

[nsf.gov]

Related - Europa Report is a pretty good sci-fi film that explores what first contact could be like. Drama of course, but still fun.

Squid-like heptapods, but our first contact might be with some form of micro-organism.

In gross characteristics, convergent evolution suggests that space travelers would look like us. (similar in silhouette) As sharks look like dolphins. Upright, sense organs at the high point, the details of joints and insulation probably very different since these would depend on their ancestors. I think we would quickly recognize they were intelligent tools makers. Of course their home would have similarly complex organisms of many kinds.

The brain's higher functions and the design of the human hand were co-causal in their evolution.

That is, the better and more versatile the tool, the more powerful a computer can be 'justified' to run it.

This and some other reasons make it seem like Anthropomorphism is at least 'in the cards' when it comes to an intelligent species.

Don't have a clue.But sending nude pictures off us,our music would probably be the reason they fly by.

They must all have a thumb

It's an interesting question. Their bodies and physiology can only reflect their environment so if they need eyes, ears and a nose they'll have them in some fashion. But it would depend on where and what they're from.

The other thought that crosses my mind with sort of question is would they conceptulise things the same way we do. Different cultures on this planet can have some profound difficulties in this regard when trying to communicate.

I think it highly unlikely that we're alone in the universe whether it's intelligent life (how we understand it) or just microbic life but I'm more and more sure that we haven't been visited, at least not that we're aware of. Any sensible alien race would and should give us a wide birth at this stage in our evolution.

If they were the size of viruses or bacteria, we might not even recognise them. Somehow people's ideas of aliens are in line with religious views prevailing in the western cultures. There could be aliens of all sorts from all sorts of different environments. Perhaps some forms could exist in space. Most people come up with very pedestrian models of alien/extraterrestrial lifeforms. Doesn't that remind people of how humans invented their gods?

You ought to read some Frederich Pohl, or the kirlian aura series by Piers Anthony for completely NOT anthropomorphic depictions of alien species .

I believe that the odds of us finding other primate-like species is quite high, actually. Assuming, of course, that life evolved on earth due to a specific set of circumstances as most scientists believe (thermal vents in the ocean + organic ingredients = first psuedo-life)

If this is the law of the universe on how life starts, I could imagine it happening elsewhere about the same way, with varying degrees of differential.

Where would the dinosaurs be had they not been wiped out by a meteor? Probably still mostly gone... as the climate of Earth changed so the surviving species of reptiles had to severely scale down...

But rodents thrive in a number of environments. So many, in fact, that they are the common precursors to felines, canines, bovine, primate, equine... etc.

So I imagine what it comes down to is an evolutionary cold war between various mammals on who develops the most complex brain first. This would be entirely dependent on the situation.

Our ancestors evolved because we lacked the claws, brute strength, and ability to quickly procreate. We started walking upright so we could run faster when trees weren't available. I'd imagine if any mammalian species were faced with a similar experience, and were omnivores, they'd evolve similarly. All those vitamins and minerals from leafy greens, fruits, nuts, grains, fish, reptile, avian, etc... had to play a role in our developing a highly complex brain. Especially when we started cooking them.

So back to the OP. I beleive aliens may look like a more evolved version of their home planet's mammals, and to a lesser extent, their birds, reptiles, amphibians, and marine life, in that order.

While it's entirely possible that there will be plant people and psionically comminucative gas-entities, I'm assuming the vast majority of naturally evolving life will look quite similar to life on Earth.

Assuming life started here and wasn't seeded. If life started elsewhere and came to earth... all bets are off.

It’s pointless speculating. There are far too many variables; environment, biochemistry, climate to name but three. But it’s safe to assume they’d have legs, although they may not, but some natural means of mobility. Some kind of manipulatory limbs. A large brain or equivalent (unless they were a hive species, possibly). The ability to cooperate, and probably compete.
Aftrr that, anyone’s guess is as good as the next SF writer’s.

They might look like this.

[goo.gl]

Interesting to think about the consciousness of other aliens.

If you notice, most people who believe in god are just athropomorphizing nature.

That's why I like that episode of ST:TNG that takes care of that issue, "The Chase."

They'd almost have to be ugly to us and us to them. Hands are relatively necessary for advanced tools and equipment so they would likely have something like that. Other than that, who knows?

I guess we have only fairly recently realized how incredibly intelligent octopuses are

I highly doubt any will visit.

Given the vast spectrum of possibilities, we will probably not recognize them as life forms. Or perhaps they are already here in a form we may not expect ........

Mostly because they're played by humans but also because they have to be relatable to humans for dramatic reasons.

Far more interested in the differences in the way they might think. Imagine we reach out and communicate with a species that form social colonies like bees or ant. And that their sense of identity is with the hive rather than the individual organism.

I keep running across tidbits about octopus having alien DNA. I have to read more about it but I might put my money on them looking more like that

I never understood why some creature from another planet should be interested in our planet, unless it is the same environment as theirs. And why are they always portrayed being ugly and slimy.

Maybe the aliens depicted here are a little too anthropomorphic...

I love this thought. I'm inclined to think of Douglas Adams, whose aliens were all over the place (the Huluvoo, for example, or even the talking mattress). I don't think we can help anthropomorphizing, though. We're wired that way.