Convert the point $(-4,0)$ in rectangular coordinates to polar coordinates.  Enter your answer in the form $(r,\theta),$ where $r > 0$ and $0 \le \theta < 2 \pi.$
We have that $r = \sqrt{(-4)^2 + 0^2} = 4.$  Also, if we draw the line connecting the origin and $(-4,0),$ this line makes an angle of $\pi$ with the positive $x$-axis.

[asy]
unitsize(0.5 cm);

draw((-5,0)--(5,0));
draw((0,-1)--(0,5));
draw(arc((0,0),4,0,180),red,Arrow(6));

dot((-4,0), red);
label("$(-4,0)$", (-4,0), S);
dot((4,0), red);
[/asy]

Therefore, the polar coordinates are $\boxed{(4,\pi)}.$