In Denmark, some professions are regulated by law, e.g. lawyer, authorised psychologist, financial advisor, dentist, and doctor. If you want to work in Denmark within a regulated profession you must apply for a Danish authorisation or similar official approval. The conditions and rules depend on the Danish legislation for the individual profession. 

You can see a list of the professions that are regulated by law on the Ministry of Higher Education and Science's website

You can also read more about how to apply for an authorisation, i.e. how you get permission to work within a profession regulated by law

If you have been trained as a medical doctor, a dentist or a nurse in a country other than Denmark, you can apply for a residence permit in Denmark which makes it possible for you to learn Danish, pass the professional tests etc. that are necessary in order to obtain a Danish authorisation.

If the Danish Patient Safety Authority has assessed that you are covered by the authorisation process for specifically requested healthcare professionals, you are allowed to also apply for a residence permit in Denmark.

Read the guide on how to apply for a residence permit for obtaining a Danish authorisation