All monitors can be calibrated, because the calibration profile is controlled and applied at the operating system level. The question is to what extent can the monitor be calibrated. However, as to how much the calibration will improve the colour from your monitor depends on the colour gamut that your monitor is capable of displaying.
Also, what Sammy888 said about printers and external parties is correct. Just because you calibrate does not mean that they do so, or that their calibration is consistent with yours (although to a large extent, if they did calibrate properly, the colours you see should be in the same ballpark as what they see). Even between different monitors, the colours may still look different after calibration because each monitor's colour gamut is different.
But if you can afford to do so, do calibrate your monitor. I think at the very least, it gives you confidence that you are not the source of the problem when there is a dispute over the output you are producing. Also, when other people who also calibrate their monitors see your photos, they should be able to see more or less the same colours that you intended.