Q: People are asking me to preside for a “teaching Mass” when I’ll interrupt the service at times to explain what is happening. Have you ever done these?
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A: I confess I did as a younger priest, but I decline any more. Teaching belongs outside the liturgy.
That said, GIRM 31 allows four places where the priest may offer commentary.
“He is permitted, furthermore, in a very few words, to give the faithful an introduction to the Mass of the day (after the initial Greeting and before the Penitential Act), to the Liturgy of the Word (before the readings), and to the Eucharistic Prayer (before the Preface), though never during the Eucharistic Prayer itself; he may also make concluding comments regarding the entire sacred action before the Dismissal.”
You could build on the catechesis outside of Mass by explaining a little more of what is happening within the Mass at these points. But overall, I’d keep the events separate.