In theory, yes. The unlock thing basically means that your phone isn't "locked" to that carrier that you bought it from. once it is unlocked, it should theoretically work with any compatible GSM carrier. I say theoretically, because your phone must support the network bands that the carrier uses in the area you're in.
As an example: I took my Verizon LG G3 (unlocked) to Mexico a few years ago. I used Movistar there. However, my phone wasn't compatible with the 4G bands they use, so I never got a 4G signal, even though there was 4G coverage in most of the areas I was in.
Additionally, it may be possible that some carriers use different network bands in different places. So it may be possible that in one area you are in, you get 4G coverage, but in another area, they use another band that your phone isn't compatible with, and you might not get 4G coverage.
You can try a website like willmyphonework.net to see if it is compatible with the carriers in whatever country you plan on visiting.