A Research Study to Check the Safety of NNC9836-0001 When Given to Healthy Participants and Participants With Type 2 Diabetes

The purpose of this clinical study is to determine if the study medicine NNC9836-0001 is safe and tolerable in healthy participants with overweight or obesity or who have type 2 diabetes (T2D). Participants will either get the study medicine NNC9836-0001 or placebo. Which treatment participants get is decided by chance. NNC9836-0001 is a new medicine aimed to treat type 2 diabetes.

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 suitability for the study. * Male or female (sex assigned at birth, inclusive of all gender identities). Metabolically healthy participants with overweight or mild obesity: * Age 25 to 59 years (both inclusive) at the time of signing the informed consent. * Body Mass Index (BMI) 25 to 34.9 kilogram per square meter (kg/m\^2) (both inclusive) at screening. * Considered to be generally healthy based on the medical history, physical examination, and the results of vital signs, electrocardiogram (ECG), and clinical laboratory tests performed during the screening visit, as judged by the investigator. Participants with type 2 diabetes: * Age at the time of signing the informed consent: Age 25 to 69 years (both inclusive) * BMI at screening: BMI 27 to 39.9 kg/m\^2 (both inclusive) * Diagnosed with T2D greater than equal to (≥) 180 days before screening. * Concomitant medications before screening: Stable (as judged by the investigator) with daily dose(s) on monotherapy (metformin, sodium-glucose cotransporter 2 inhibitors (SGLT2i), or dipeptidyl peptidase-4 inhibitor (DPP4i) or dual therapy (metformin + SGLT2i or metformin + DPP4i)) ≥90 days before screening. or; Stable weight and stable doses of glucagon-like peptide-1 receptor agonists (GLP-1 RA) with no further titration (as judged by the investigator). GLP-1 RA ≥180 days before screening combined with daily dose(s) of either metformin or SGLT2i or dual therapy (metformin + SGLT2i)) ≥90 days before screening. * Background pharmacotherapy for all MAD cohort T2D participants should be on stable therapy for ≥90 days before screening with no initiation, discontinuation, or dose changes. * Considered to be generally healthy as judged by the investigator except for T2D-associated mild conditions under stable treatment. Exclusion Criteria: All participants: * Known or suspected hypersensitivity to study intervention(s) or related products. * Previous dose administration in this study. * Participation (i.e., signed informed consent and dosed with Investigational medicinal product (IMP)) in any other interventional clinical study within 30 days or 5 times the half-life of the drug, whichever is longest, before screening. * Any disorder, which in the investigator's opinion might jeopardise participants safety or compliance with the protocol. * Female who is pregnant, breast-feeding or intends to become pregnant or is of childbearing potential and not using adequate contraceptive method. * Minimal to mild hepatic impairment, defined as alanine aminotransferase (ALT) values greater than (\>)1.5 × upper limit of normal (ULN), aspartate aminotransferase (AST) values \>1.5 × ULN, or total bilirubin \>ULN + 20 percent (%) (except in case of Gilbert's disease, as reported by participant or in medical records) at screening. Metabolically healthy participants with overweight or mild obesity: * Supine blood pressure outside the range of 90-139 millimetres of mercury (mmHg) for systolic or 50-89 mmHg for diastolic at screening. To consider re-assessment of vital signs in case white-coat hypertension is known or suspected. * Heart rate outside the range of 45-89 beats per minute (bpm) at screening. * Unwilling or unable to refrain from use of nonprescription products within 14 days prior to start of run-in, including herbal products and nonroutine vitamins (as judged by the investigator), except the occasional use of over the counter (OTC) acetaminophen or non-steroidal anti-inflammatory drugs (NSAIDs) at their labelled doses for mild pain. * Recent (\