As the other educators mention in their answers, different Native American tribes often played a military role in imperial conflicts. However, they also played an economic role. Remember that the French and the English were very interested in the lucrative fur trade coming from the frontiers of North America. While European trappers did do some of the trapping themselves, most furs came from trade with Native Americans.

As early as the seventeenth century, the English and the French began courting various native alliances for access to the furs found in their territories. The English formed a strong trading alliance with the Iroquois, while the French traded heavily with the Huron and their allies around the Great Lakes. It did not take long for the Iroquois to look to the north in order to secure the more profitable fur trapping territories of the Huron, Ottowa, and Erie. They fought a series of wars in the mid-seventeenth century over control of parts of the Great Lakes region to gain access to these furs in order to trade them with the English.

The English were all too happy to receive more furs from lands that had previously benefited their French rivals. This loss of lucrative fur trapping territory ended up encouraging the French to push deeper into lands claimed by the English. A number of wars, beginning with Queen Anne's War and culminating in the French and Indian War, resulted, partly over granting their respective native allies access to these lands.

The topic of the role of Native Americans in the colonial or imperial wars of the 1700s can be approached from a number of perspectives.

The most direct role was through participation in armed conflicts between imperial powers. Collectively, natives served as foot soldiers, suffering large losses. Their participation sometimes resulted from assimilation with or into the colonies. Other times, they chose to fight out of political calculation (e.g. in hopes of increased sovereignty). They often tried to play the major colonial powers off each other. As more time passed and their civilization crumbled, the involvement was frequently dictated by their position of weakness: to pay off debts or simply to have access to food and other necessities of life. While they were not powerless or passive, and they sometimes mounted major armed opposition (e.g. Pontiac's Rebellion), they often had little leverage and limited choices.

Native Americans played a substantial military role in colonial warfare. There are helpful online resources, a few of which are linked below. One should keep in mind that the relationship between Europeans, colonists, and natives was multi-faceted. Interactions could be military, financial, cultural, and so forth, with no clean lines separating one form of interaction from another. Interactions persisted over centuries with different tribal and political entities. In other words, the topic is a big one.

The Native Americans also contributed to the conflicts in less direct ways: for example, colonial forces often adopted native tactics of warfare. The natives were familiar with their home terrain and, in terms of technology and supplies, were frequently at a disadvantage. These circumstances dictated guerilla warfare. The various imperial powers used these methods to varying extent, but they were embraced on a mass scale by the British colonies and, later, American revolutionaries. One could argue that the British colonists, operating from a similar position of familiarity with the terrain and relative weakness, adopted native strategies as a means of defeating the king's armies during the American Revolution.

Native Americans played a central role in the imperial conflicts of the eighteenth century from Queen Anne's War at the beginning of the century to the American Revolution. Various Indian groups formed alliances, mostly based on trade with the British, the French and the Spanish. They became quite skillful at "playing off" the sides against each other in order to secure favorable trade, help in fighting against other Indian tribes, and other motives. Indian alliances were especially crucial in the Seven Years' War (known in the colonies as the French and Indian War) from 1754-1761.  Most of the Iroquois Confederacy fought on the side of the British and the colonies, while the Huron, Algonquian and other powerful groups fought with the French. When the American Revolution broke out, most Indian tribes, with a few notable exceptions (the Catawba in North and South Carolina being the largest) fought on the side of the British, whose Proclamation of 1763 had forbidden colonial expansion over the Appalachians. The point is that Indians were not passive victims of the conflicts. They helped to shape them and to determine who won and lost them.