It's for you to read, but not as a rulebook to keep. Jesus preached it before the cross, raising the law to its full height to expose that no one can climb it, so we would stop trying and receive Him. It drives you to grace, it isn't a grace-powered to-do list.
The Grace Answer
The Sermon on the Mount gets handed to Christians as a lifestyle manual: here is how a good believer behaves, now go do it. Read that way, it is crushing, because the demands are impossible. Do not even be angry. Do not even lust. Be perfect as your heavenly Father is perfect. If that is a checklist, everyone fails it by breakfast.
The key that unlocks it is where it sits in the story. Jesus preached this before the cross, to people living under the law of Moses, and He was not softening that law. He was raising it to its full, terrifying height. The scribes had shrunk the commands down to something manageable, so Jesus pushed them back up past the roofline. “Unless your righteousness exceeds the righteousness of the scribes and Pharisees, you will by no means enter the kingdom of heaven.” That is not a motivational goal. It is a closed door, unless Someone else opens it.
What it is actually doing
The law's job was never to make you righteous. It was to show you that you are not, and to march you toward the only One who is. “The law was our tutor to bring us to Christ, that we might be justified by faith.” The Sermon on the Mount does that job better than any passage in Scripture. It sets the bar at God's own perfection so that self-effort finally collapses and you look up.
So yes, read it. Read it often. But read it as the diagnosis that drives you to the cure, not as the cure itself. When it exposes how far short you fall, it has done exactly what it was sent to do. And on the other side of the cross, the righteousness it demanded becomes the righteousness you were freely given, so that its beauty describes who you already are rather than a wall you keep failing to scale.