If you are part of an institutional church that has a pastor preach a sermon during a worship service, then I highly encourage you to speak to him about this beforehand. You don't have to ask his permission to speak during the gathering, but it would be good to do so as a matter of Christian courtesy. He may have a positive suggestion for how you can best add to the teaching time in a way that would benefit the entire church family. If he says that you cannot do this or discourages you from speaking, then ask him what biblical basis he has for doing so.
If you are part of an organic church/simple church/house church, then I encourage you to plan to ask questions, make comments, add an interpretation, etc. Be prepared to participate.
Paul tells us in I Corinthians 12 that the church body is composed of many different members that are all needed for the church. Every body part matters. When all participate the body is healthy.