Ready to hear about a balancing act?
Yes...the most common sounds come first. This is because the whole point of letters is to write and read. If, for example, you have the word, "Cat," it makes more sense for the child to be able to identify
If the child has to translate everything:
"'C' says /c/, A says /a/, and T says /t/"
...well...you can see how confusing this can get. You're doing twice the work.
The NAMES of letters come later. How much later depends on many factors, but the biggest factor usually is the exposure to it outside the classroom. Most children do not need to be specifically taught this since they see and hear it so much outside of the classroom. Other students (especially from backgrounds with families of lower educational levels) might need more direct instruction of this.
For right now, I would stick to the basic sounds. Once your child has a grasp on that, move to blends. After a while, you'll know if you need to introduce the letter names. Some teachers do this specifically as they teach sight words (which there's no "official" Montessori way to do since Italian, Montessori's main language, does not require this as much as English).