A good poem generates energy, or better yet, is energy. What does this mean? That there’s action and contrast. Movement. Transformation. To better understand, ponder the opposite: stasis, inertia. Passivity and monotony.
To make an image or idea dynamic means to give it something to spark against, to put it into contact with something else. You could try banging a flint against empty space, but nothing will come of it. Take a poem you love and examine how the sparks are created. Do the images and ideas interact, bang into each other like excited atoms, or are they each suspended in a sterile environment, cool and aloof?
I try to keep thinking about energy not only during the writing process but also (and perhaps especially) during revision. Having images and ideas already on paper to work with – to rearrange, expand upon, cut, simplify, complicate, connect – makes the job of activation easier.