Adam Clarke on Psalms 29:4

Is powerful - There is no agent in universal nature so powerful as the electric fluid. It destroys life, tears castles and towers to pieces, rends the strongest oaks, and cleaves the most solid rocks: universal animate nature is awed and terrified by it. To several of these effects the psalmist here refers; and for the illustration of the whole I must refer to the above notes on Job.

Full of majesty - No sound in nature is so tremendous and majestic as that of thunder; it is the most fit to represent the voice of God.