I could melt you could melt he could melt we could melt you could melt they could melt
V-ing form
I could be melting you could be melting he could be melting we could be melting you could be melting they could be melting
Perfect
I could have melted you could have melted he could have melted we could have melted you could have melted they could have melted
V-ing perfect
I could have been melting you could have been melting he could have been melting we could have been melting you could have been melting they could have been melting
Negation
Simple form
I couldn't melt you couldn't melt he couldn't melt we couldn't melt you couldn't melt they couldn't melt
V-ing form
I couldn't be melting you couldn't be melting he couldn't be melting we couldn't be melting you couldn't be melting they couldn't be melting
Perfect
I couldn't have melted you couldn't have melted he couldn't have melted we couldn't have melted you couldn't have melted they couldn't have melted
V-ing perfect
I couldn't have been melting you couldn't have been melting he couldn't have been melting we couldn't have been melting you couldn't have been melting they couldn't have been melting
Interrogative form
Simple form
could I melt? could you melt? could he melt? could we melt? could you melt? could they melt?
V-ing form
could I be melting? could you be melting? could he be melting? could we be melting? could you be melting? could they be melting?
Perfect
could I have melted? could you have melted? could he have melted? could we have melted? could you have melted? could they have melted?
V-ing perfect
could I have been melting? could you have been melting? could he have been melting? could we have been melting? could you have been melting? could they have been melting?
Interro-negative form
Simple form
couldn't I melt? couldn't you melt? couldn't he melt? couldn't we melt? couldn't you melt? couldn't they melt?
V-ing form
couldn't I be melting? couldn't you be melting? couldn't he be melting? couldn't we be melting? couldn't you be melting? couldn't they be melting?
Perfect
couldn't I have melted? couldn't you have melted? couldn't he have melted? couldn't we have melted? couldn't you have melted? couldn't they have melted?
V-ing perfect
couldn't I have been melting? couldn't you have been melting? couldn't he have been melting? couldn't we have been melting? couldn't you have been melting? couldn't they have been melting?