Most crucial part here is CONFIDENCE and balanced posture – if you get that right, everything else regarding movement will be only icing on the cake.
Movement gives you an amazing opportunity to build a relationship with the audience – step into their space, be open to everyone, and communicate openess and trustworthiness with your presence.
Purposeful movement means that movements that you make on the stage (e.g. walking in a certain direction, coming closer or stepping further away from the audience, making one step forward with each statement you make, or hitting the floor loudly with your foot) has a clear purpose – that purpose might mean grabbing the attention of the audience, directing the level of the energy in the room, showing determination, underlining some crucial statement, etc.
By purposeful movement you will not distract the audience from your speech, and at the same time you will underline the most important points and break the flow and monotony to do nice smooth transition between different parts of the speech.
Movement on the stage obviously depends a lot on the individual style of the speaker. Too much dynamics can distract, and many people have a habit of walking up and down the stage without a clear purpose or goal. That is why a good way to start controlling your movement is to “ground” yourself – stand still, put your feet parallel one to another in the width of your shoulders and imagine roots growing out of your feet into the floor. When you want to do a transition, do a short walk in one clear direction. When you want to convince your audience of something, step towards the audience.
Use your movement to underline your words.
It is not about how much confidence you really have – it is about how much confidence you project onto your audience That means that the most important part is to keep an open confident posture, and kick out any excessive movement that we tend to do as a result of being nervous. It also means that you must learn to enjoy the silence on the stage, without a constant need to fulfil any moment of silence with filler-words (uuuhm, ahhs, etc.) or with talking too fast and too much.
Check out this post on how to handle pre-stage fear: Dealing with stage fear
Great example of a confident speaker, radiating strength and assurance, is Barack Obama in his inauguration speech:
Posture is the first thing that your audience notices once you show up on stage, and often already when you show up in the room. It is first message that they get from you, and therefore extremely important. Balanced posture means that you straighten your back, put your shoulders up, open your chest and breathe deep and calm. It also means that you are not leaning to any side, keeping your hips parallel and balanced , and your feet parallel in the width of the shoulders. It also means that you are not playing with your arms, crossing them, or desperately searching for the ways too keep them busy, but you keep them or relaxed and parallel to your body, or used in a meaningful gestures.