This paper formalizes metrical grid theory (MGT, Prince, 1983; Hayes, 1995) and studies its expressive power. I show that MGT analyses of a certain form can describe stress systems beyond the input tier-based input strictly local functions proposed by Hao and Andersson (2019), but conjecture that such analyses do not describe systems beyond the input tier-based strictly local languages of Baek (2018). These results reveal fundamental differences between the three formalisms.