Can micro nutrients be used in essential activities in plants? If so, mention a few elements?

Dear student.

Yes, micronutrients are involved in essential activities in plants. A few examples are listed below.

Iron (Fe) and Molybdenum (Mo) is essential for nitrogen fixation.
Chlorine (Cl) helps in the process of photosynthesis.
Zinc (Zn) helps in photosynthesis, energy production and regulation of growth.

Regards.