When the liquid metal Terminators change their appearence, does the skin portion feel like skin and their clothing feel like clothes, or do the Terminators feel like liquid metal no matter what they outwardly morph into?
Theoretically, for the T-1000 to be able to blend in they would need the ability to mimic the appearance and texture of human skin and fabrics. As advanced infiltration units it is hard to imagine they would NEVER come into physical contact with humans where it would not be more advantageous to effectively decieve the humans, let them live and advance their goals of further infiltration.
I imagine if a T-1000 could NOT change its texture and simulate human flesh and clothing, its value as an infiltration unit would be severely compromised in the tight quarters the future humans were living in under their occupation by Skynet.
The T-1000 can also change its color and texture to simulate flesh, clothing, and other nonmetallic materials. It is capable of accurately mimicking voices as well, including the ability to extrapolate a relatively small voice sample to generate any words or inflections it requires. Wikipedia
Since they are using nanotechnology, there is no reason to believe they could not accurately represent any basic matter they were familiar with and had specifications to represent. The scale of nanotechnological machines would allow them to physically recreate any known fabric or metal and actually BE the material they were presenting especially to human senses.
As an aside, they have to be capable of time traveling and by that logic, they must be able to replicate a clearly organic state (to be able to cover themselves completely) and make the time travel journey possible. In Terminator 2: Judgement Day, the T-1000 uses the same technology to arrive in the past as was used by the previous T-800 series cyborg.
An aware person might notice (especially if this is not part of the infiltration software the T-1000 uses) the lack of physical dirt or more complex physical/chemical traces on the "clothing" of the infiltrating unit. If they were not designed for complex organic molecules they may not be able to replicate such scents easily, if at all.
In The Sarah Connor Chronicles, Savannah, the daughter of a woman who has been replaced by a T-1000, remarks that her ersatz mother's lap is cold. This is a clear indication that the T-1000 can't completely hide its metallic nature, the thermodynamic properties of metals being quite different than cloth-covered flesh. So from this we can gather that T-1000s definitely feel like metal even if they don't look like it.
Though they're described as "liquid metal", the only plausible technology for such a thing would be nanotechnology: little microscopic robots. These robots might be made of metal, but more likely would be some carbon/organic foundation. The latter could theoretically still give the mercury sheen seen in the movie, and be able to give the appearance/color/texture of anything needed besides by relying on structural coloration.
As such, I speculate that during the transition phase, the T1000 wouldn't feel like metal at all, either solid metal or mercury (though, no one under the age of about 55 knows what it's like to play with the stuff or feel it with their bare fingers). Instead, it would probably feel (texture-wise) like the wings of a butterfly or peacock feather, but very warm (lots of energy) and with a bizarre fluid motion that we probably would find it impossible to imagine.
This is all highly speculative, of course, I am unaware of anything supporting this in canon, except for that novelization I read back in high school. It gave one or two sentences more detail than Arnie spoke, and relied less on the "liquid metal" and more on the "nanobots" angle. Escapes me at the moment, but I think it was written by Foster.
The real question you need to ask yourself is: What does metal feel like, and can I differentiate that sensation from other materials when I touch it?
Here is a simple experiment that can be done to answer the question.
Get three objects of similar shape and size. Get one made of glass, One of smooth plastic, and one made of metal. Close your eyes and have a helper present a random object to you to touch. Don't examine the object, just use a finger and make contact with the object. This is to isolate the sensation you get when you make contact. The point of the experiment is to see if you can sense what material is present by simply touching it.
When I did this experiment, I was unable to conclusively say that one object was definitely made of Glass, Plastic or Metal.
I was only able to determine that the object was solid, and it's relative temperature compared to the other objects.
Because it's up for speculation what the exact power source for a T-1000 is, we do not know if it is endothermic or exothermic. We don't know if it is warm or cold to the touch.
Also, we don't know how viscous the liquid metal is. It may be similar glass, which technically is liquid, but has a tactile sensation of a solid. A liquid that close to a solid state would require substantial energy to move, but something like silly putty or play dough would be a good analogue. It's easy to alter the shape of those materials, and they can hold shape at room temp.
I would conclude that it wouldn't feel like metal when changing shape in the spirit of the above mentioned experiment.
However, whatever it takes the form of, there may be a very close match in texture and tactile sensation. Clothing may feel like silk no matter what material it's supposed to be, and knives, well, that shouldn't need any explanation ;)
Liquid metal terminators likely "feel" as if they are human, at least by texture if not temperature. They have been known to time travel, which requires organic tissue at least on their outsides. Because their cores are made of steel, I doubt they would be very warm and friendly, unless artificially heated.