gods
One of the main differences about gods and in the Viking age and gods in modern society is that all Vikings believed in the same gods but in modern society there is a big range of religions and people believe in different gods depending on the religion. For example, in today's society there are Christians, Buddhists, Muslims, Hindus, and Jewish religions as well as others and they don't have the same gods. Christians worship God, Buddhists worship Buddha, Hindus worship a range of gods, etc.
Valhalla and heaven
Valhalla (Viking heaven) is unlike the Christian image of heaven in many ways. These include the fact that in the Christian idea of heaven it is in the clouds instead of in a hole, which is where Valhalla is. Also, the ways of getting into "heaven" are different from getting into Valhalla. To get into heaven in the Christian religion is to be a good person, have good morals and follow the Christian faith, including follow the ten commandments. By comparison, to get into Valhalla you have to be a skilled or well-known warrior because in Valhalla every day you must fight in the plains of Asgard and eventually help Odin defeat the fox, Fenrir. In Viking culture there is quite a lot of focus on what you do in Valhalla, the fighting but also what you eat and drink. By comparison, in the Christian idea of heaven is to go there for an everlasting life, to meet dead ancestors, and to not go to hell.
Religious leaders
Viking religious leaders were very unlike today's religious leaders in many ways. One of these include that in Viking society the leaders ("priests") often worked other jobs besides being religious leader such as politicians or judges. By contrast, in modern society priests or other religious leaders generally work full-time in that job and in some societies it would also be illegal or considered wrong to mix religious leadership and jobs like being a judge. For example, in the the United States the is church is separate from the state. Another difference is that in today's religious culture there is usually a structure of leaders, e.g., the pope, bishops, cardinals whereas in Viking times there was no centralised leadership structure and it was mainly focused on individuals with scattered roles. There are a couple of similarities between religious leaders in Viking and modern times. One of these is the fact that both in Viking and modern times the head of the household (parents) are responsible for religious leadership within the family. Likewise, religious leaders in modern society are not expected to be able to cure disease or maintain good health which was the same as in Norse religion.