Patrick Henry was an anti-federalist and he gave a lot of speeches and wrote many papers that extolled the virtues of a confederation. In a confederation, the states have sovereignty. Those speeches, which occurred almost immediately after the Constitution was ratified, is where his warnings can be understood.
Henry, like all anti-federalists, believed that a strong federal government would strip the people and the states of their rights and freedoms. Henry warns that the position of president, the roles of which are pretty vague in the Constitution, could easily morph into a monarch. The monarchy, or parliamentary monarchy more specifically, is the form of government that Americans had just shed blood to break free from. Patrick Henry believed that with the endorsement of a Constitution that gave significant power to a central government, the possibility existed that this same body would usurp this power through taxation and other means. In other words, the Americans would have traded a tyrant an ocean away for one that existed on the same continent.
Patrick Henry was a revolutionary that was very much in favor of America becoming independent from Great Britain. He warned colonists that their rights were being taken away from Great Britain, and that they were not treated as they should be. he urges the colonists to rebel and fight for independence so that their liberties can be restored.
i think he is the guy who said "the british are coming"