Hi,
I'm afraid there is some confusion here. The initial question was "can you tune a mic" and the answer was "apply EQ". Applying EQ, regardless of its software or hardware nature, is part of the mixing phase and it really is meant to enhance (or fix, in the worst cases) the initial performance. The signal that was caught by the mic in the first place can be processed afterwards, or even in real-time during recording/broadcasting if needed (which is generally not recommended for recording as it cannot be undone), but the mic itself cannot "tune" or "be tuned", it is meant to catch the sounds in the most faithful fashion.
Now, a mic can be "voiced" and that requires some expertise in electronics and replacing of specific parts, but this only change the sound in a very subtle way and I'm guessing this is not what you were referring to. A microphone is basically converting sound waves into electrical energy, and it is usually designed in a way that it allows faithful reproduction of the sound source. Therefore if the sound source is a singer who sings out of tune, it will hear and converts this into a very faithful, out of tune recording/broadcasting. If the sound source is a crappy guitar amp, the unprocessed signal will be just as crappy.
During the mixing phase it is possible (and very common in professional studios actually) to apply tuning to the voice, using dedicated software. You've probably heard of Autotune but there are a number of similar solutions. There are a wide variety of treatments and processes that can be applied, the most commonly used for vocals being compression, equalization and reverb.
If you could clarify and elaborate on your initial question by explaining what is the goal you're aiming at, we will probably be able to answer more specifically.