Checkbox checked if boolean is true with Angular2

you are missing square bracket around checked

<input type="checkbox" [checked]="person.is_adult">

Hope this helps!!

{{}} does string interpolation and stringifies true and false and Angular by default uses property binding and I assume the property expects boolean values not strings:

<input type="checkbox" [checked]="person.is_adult">

This might work as well

<input type="checkbox" attr.checked="{{person.is_adult}}">

because with attribute binding the browser might translate it from the attribute (which can only be strings) to boolean when reading it into its property.

It is also checked instead of value

You can also use ngModel

<input type="checkbox" [ngModel]"person.is_adult" name="isAdult">
<input type="checkbox" [(ngModel)]"person.is_adult" name="isAdult">

for one-way or two-way binding.
Ensure your have the FormsModule imported if you use ngModel.