Why are mantras powerful?

Could you elaborate on the profound influence of mantras? How do they possess such remarkable potency? What is the essence of their strength? Do they harness some unseen energy or resonate with a deeper truth? Are they simply a psychological tool, or do they possess a more tangible, metaphysical quality? How do they impact our minds and emotions, leading to positive changes in our lives? I'm intrigued by the concept and would love to understand the science, if any, behind their effectiveness.