MethodNotAllowedHttpException laravel 5

Why am I getting this error?

Routes:

Route::group(['prefix'=>'admin','middleware'=>'auth'],function(){
    Route::get('/',['uses'=>'Admin\IndexController@index','as'=>'adminIndex']);
    Route::resource('/products','Admin\ProductController');
});

Form:

{!! Form::open(['url' => route('admin.products.edit',['products'=>$product->id]),'class'=>'form-horizontal','method'=>'POST']) !!}
                    
                    {!! Form::button('Edit', ['id'=>'submit','type'=>'submit']) !!}
                    {!! Form::close() !!}

Also, when I'm trying to get list of routes by typing php artisan route:list, I'm getting error:

[Symfony\Component\HttpKernel\Exception\HttpException]

What's the problem?

via Batmannn