.obj model not appearing

I just want to load a three.js example called cerberus. Code is:

const objLoader = new OBJLoader();
objLoader.load( '/models/obj/cerberus/Cerberus.obj', function(object) {
     scene.add( object );

Do i have to load .mtl file too?

No, it also works without the MTL file. Just drag’n’drop the OBJ into the editor to verify this.

Model are often not being visible because of bad camera configuration or missing lighting. How does the respective setup in your app looks like?

I have

const camera = new THREE.PerspectiveCamera( 75, window.innerWidth/window.innerHeight, 1, 2000 );
camera.position.z = 5;

but no light. Maybe this is the fault

I guess so. Try to add some lights and check it again.