It's very simple to play this. You just need four chords! Fm, G, Am, C
This is how I play it. 

   Fm (133111@1)             G (320003@1)                   Am (x02210@1)         
He ate my heart, He a-a-ate my heart, He ate my heart
   CHe (x32010@1)a-a-ate my heart out
(You amaze me)
        FmLook (133111@1)at him
        GLook (320003@1)at me
            AmThat (x02210@1)boy is bad
            CAnd (x32010@1)honestly
       Fm (133111@1)       GHe’s (320003@1)a wolf in disguise
                 Am (x02210@1)                      CBut (x32010@1)I cant stop staring in those evil eyes
F (133211@1)                         G (320003@1)                  
I asked my girlfriend if she'd seen you round before
Am (x02210@1)                           CShe (x32010@1)mumbled something while we got down on the floor baby
F (133211@1)                        G (320003@1)We might've f@#!ed not really sure, don't quite recall
Am (x02210@1)                             C (x32010@1)            GBut (320003@1)something tells me that I've seen him, yeah
                F (133211@1)   GThat (320003@1)boy is a monster
M-M-M-Monster
               Am (x02210@1)    C (x32010@1)                
That boy is a monster
M-M-M-Monster
                 F (133211@1)  GThat (320003@1)boy is a monster
Monster
                Am (x02210@1)    GThat (320003@1)boy is a monster
er-er-er-er

REPEAT THE REST AS SHOWN ABOVE! 

He ate my heart
(I love that girl)
He ate my heart
(Wanna talk to her, she's hot as hell)

He licked his lips
Said to me
Girl you look good enough to eat
Put his arms around me
Said Boy now get your paws right off me
I asked my girlfriend if she'd seen you round before
She mumbled something while we got down on the floor baby
We might've fucked not really sure, don't quite recall
But something tells me that I've seen him, yeah


That boy is a monster
M-M-M-Monster
That boy is a monster
M-M-M-Monster
That boy is a monster
Er-er-er-er
He ate my heart
(I love that girl)
He ate my heart
(Wanna talk to her, she's hot as hell)

He ate my heart
He ate my heart
Instead he's a monster in my bed

I wanna Just Dance
But he took me home instead
Uh oh! There was a monster in my bed
We french kissed on a subway train
He tore my clothes right off
He ate my heart the he ate my brain
Uh oh uh oh
(I love that girl)
(Wanna talk to her, she's hot as hell)

That boy is a monster
M-m-m-monster
(Could I love him?)
That boy is a monster
M-m-m-monster
(Could I love him?)
That boy is a monster
M-m-m-monster
(Could I love him?)
That boy is a monster