In World War II, Canada played a role that is no different that the role that many other countries did -- their role was to send soldiers and materiel to be used in the war. Canadians participated in fighting in all theaters of the war. This included the D-Day invasion in which Canada played a major role. So Canada's role was the same as every other country's role.
Canada was not the most populous or the biggest country in WWII and so its involvement was not as significant (in absolute terms) as that of the United States, for example. However, over 1 million Canadians served in uniform and almost 100,000 were either killed or wounded.
During World War Two, Canada contributed domestically by helping the Allies and providing them with a training ground and supplied them in the war. Also, Canada started focusing on the Navy and Air Force which helped them with their economy. Canada was involved in many battles and created military equipment’s for Canadians. Canada became a more powerful nation and played many important roles during battles such as Battle of Atlantic. Canada was involved domestically and internationally and had an impact on Canada in World War II.
Almost from the beginning Canadians were in the thick of the fighting—in the air. In that element the Dominion made its most striking contribution to the general war effort. On the outbreak of hostilities, the British Commonwealth Air Training Plan was established in Canada to develop the air forces of Britain, Australia, and New Zealand, as well as of Canada. It was under the direction of the Royal Canadian Air Force, and it cost the Canadian government well over 1.5 billion dollars.