How to draw a 3D line using metalkit

Question

I'm trying to draw a 3D line using metalkit in iOS, I added two vertices

 [{ .position = {  1,  1, -1, 1 }, .color = { 0, 0, 1, 1 } },
        { .position = { 1, 1, 1, 1 }, .color = { 0, 0, 1, 1 } }]

I'm applying modal matrix with rotation angle.

const matrix_float4x4 modelMatrix = zRot;

But the line is rotating continuously, i tried using translation matrix but no difference i observe.

Actually my task is to draw a line in 3D for augmented reality, placing markers using latitude and longitude with path along them.

As a first step i'm trying to draw a 3D line using metal. Plz Refer any example for drawing 3D line using metalkit most of the examples are in triangles.