A Research Study to Evaluate the Safety of NNC1679-0001 When Given to Healthy Participants and Participants With T2DM

Inclusion Criteria: All participants * Informed consent obtained before any study-related activities. Study-related activities are any procedures that are carried out as part of the study, including activities to determine eligibility for the study. * Male or female (sex at birth) of nonchildbearing potential. * Age 18-64 years (both inclusive) at the time of signing the informed consent. Healthy participants * Body mass index (BMI) 18.5-29.9 kilograms per square meter (kg/m\^2) (both inclusive) at screening. * Glycated haemoglobin (HbA1c) lesser than or equal to (\<=) 6.4 percent (%) (47 \[millimoles per mole\] mmol/mol) at screening. * Considered to be generally healthy based on the medical history, physical examination, and the results of vital signs, electrocardiograms (ECG), and clinical laboratory tests performed during the screening visit, as judged by the investigator. Participants with Type 2 Diabetes Mellitus (T2DM) * BMI 20.0-34.9 kg/m\^2 (both inclusive) at screening. * HbA1c 6.3-8.5% (45.4-69.4 mmol/mol) at screening. * Diagnosed with T2DM greater than or equal to (\>=)180 days before screening. * Stable (as judged by the investigator) daily dose(s) of metformin or combination of metformin and dipeptidyl peptidase IV (DPP-4) inhibitors \>= 90 days before screening. Exclusion Criteria: All participants * Screening alanine aminotransferase (ALT) values greater than (\>) upper limit of normal (ULN) +10%, aspartate aminotransferase (AST) values \>ULN +20%, o…