What is the role of interest groups in our modern democracy?

One role interest groups play in modern democracy is to lobby elected officials to support policies that the interest group supports. For example, the National Rifle Association will lobby Congress to defend gun control laws. The National Education Association will lobby Congress to support policies that positively impact public education. When many members of an interest group contact their elected representatives, it puts pressure on the elected official to do what the majority of his or her constituents want him or her to do.
Another role that interest groups play is that they can work to help a candidate get elected. These groups may contribute money to a candidate’s campaign. They can encourage their members to do the same. They will produce television commercials, printed materials, and make phone calls on behalf of a candidate. Sometimes, interest groups will run negative ads against the opponent of the candidate they are supporting. Sometimes, the candidate welcomes this support. At other times, the candidate may not ask for or may not want this support.
Interests groups may try to educate the public regarding an issue of importance to the group. Environmental groups may hold meetings, lectures, or educational forums to inform the public about the positive and negative impacts of a proposed policy or a bill before the legislature. These groups are trying to get people to see the issue from their point of view. These efforts may lead to more people who will support the group and the ideas for which it works.
https://journalistsresource.org/studies/politics/finance-lobbying/the-influence-of-elites-interest-groups-and-average-voters-on-american-politics/