God has not only promised us signs and wonders, He has instructed us to use them (display them) as we go to do His will (preach deliverance to those in captivity and help them come out of bondage).
Exodus 4:21
21 The Lord said to Moses, “When you return to Egypt, see that you perform before Pharaoh all the wonders I have given you the power to do. But I will harden his heart so that he will not let the people go.
Mark 16:15-18
15He said to them, “Go into all the world and preach the gospel to all creation.
16 Whoever believes and is baptized will be saved, but whoever does not believe will be condemned.
17 And these signs will accompany those who believe: In my name they will drive out demons; they will speak in new tongues;
18 they will pick up snakes with their hands; and when they drink deadly poison, it will not hurt them at all; they will place their hands on sick people, and they will get well.”