Your general terms of employment are predominantly regulated by collective agreements concluded by the social partners: the trade unions and employer’ associations.
The trade unions act and negotiate on your behalf to secure you the best possible salary level and working conditions. Being a member of a trade union is very common in Denmark and can provide you with a series of employment- and career-related legal support and services you may need e.g. guidance regarding individual employment contract, salary, industrial accidents and injuries.
In order to sign up for an unemployment insurance fund, you are not obligated to become a member of a trade union.
For more information and for trade unions with English websites, please have a look at: https://www.workindenmark.dk/Working-in-DK/Trade-unions and http://www.worktrotter.dk/component/content/article/177-trade-unions-work-copenhagen-denmark.html