diff --git a/src/Expression.jl b/src/Expression.jl
index 68fd8818..9e7325a6 100644
--- a/src/Expression.jl
+++ b/src/Expression.jl
@@ -31,22 +31,24 @@ import ..SimplifyModule: combine_operators, simplify_tree!
 struct Metadata{NT<:NamedTuple}
     _data::NT
 end
-_data(x::Metadata) = getfield(x, :_data)
+unpack_metadata(x::Metadata) = getfield(x, :_data)
 
-Base.propertynames(x::Metadata) = propertynames(_data(x))
-@unstable @inline Base.getproperty(x::Metadata, f::Symbol) = getproperty(_data(x), f)
-Base.show(io::IO, x::Metadata) = print(io, "Metadata(", _data(x), ")")
+Base.propertynames(x::Metadata) = propertynames(unpack_metadata(x))
+@unstable @inline function Base.getproperty(x::Metadata, f::Symbol)
+    return getproperty(unpack_metadata(x), f)
+end
+Base.show(io::IO, x::Metadata) = print(io, "Metadata(", unpack_metadata(x), ")")
 @inline _copy(x) = copy(x)
 @inline _copy(x::NamedTuple) = copy_named_tuple(x)
-@inline _copy(x::Nothing) = nothing
+@inline _copy(::Nothing) = nothing
 @inline function copy_named_tuple(nt::NamedTuple)
     return NamedTuple{keys(nt)}(map(_copy, values(nt)))
 end
 @inline function Base.copy(metadata::Metadata)
-    return Metadata(_copy(_data(metadata)))
+    return Metadata(_copy(unpack_metadata(metadata)))
 end
-@inline Base.:(==)(x::Metadata, y::Metadata) = _data(x) == _data(y)
-@inline Base.hash(x::Metadata, h::UInt) = hash(_data(x), h)
+@inline Base.:(==)(x::Metadata, y::Metadata) = unpack_metadata(x) == unpack_metadata(y)
+@inline Base.hash(x::Metadata, h::UInt) = hash(unpack_metadata(x), h)
 
 """
     AbstractExpression{T,N}
@@ -216,7 +218,9 @@ end
 Create a new expression based on `ex` but with a different `metadata`.
 """
 function with_metadata(ex::AbstractExpression; metadata...)
-    return with_metadata(ex, Metadata((; metadata...)))
+    return with_metadata(
+        ex, Metadata((; unpack_metadata(get_metadata(ex))..., metadata...))
+    )
 end
 function with_metadata(ex::AbstractExpression, metadata::Metadata)
     return constructorof(typeof(ex))(get_contents(ex), metadata)
@@ -246,7 +250,13 @@ end
 function get_variable_names(
     ex::Expression, variable_names::Union{Nothing,AbstractVector{<:AbstractString}}=nothing
 )
-    return variable_names === nothing ? ex.metadata.variable_names : variable_names
+    return if variable_names !== nothing
+        variable_names
+    elseif hasproperty(ex.metadata, :variable_names)
+        ex.metadata.variable_names
+    else
+        nothing
+    end
 end
 function get_tree(ex::Expression)
     return ex.tree
diff --git a/src/ParametricExpression.jl b/src/ParametricExpression.jl
index 16d27254..854e28d7 100644
--- a/src/ParametricExpression.jl
+++ b/src/ParametricExpression.jl
@@ -5,7 +5,8 @@ using ChainRulesCore: ChainRulesCore as CRC, NoTangent, @thunk
 
 using ..OperatorEnumModule: AbstractOperatorEnum, OperatorEnum
 using ..NodeModule: AbstractExpressionNode, Node, tree_mapreduce
-using ..ExpressionModule: AbstractExpression, Metadata, with_contents, with_metadata
+using ..ExpressionModule:
+    AbstractExpression, Metadata, with_contents, with_metadata, unpack_metadata
 using ..ChainRulesModule: NodeTangent
 
 import ..NodeModule:
@@ -63,7 +64,6 @@ mutable struct ParametricNode{T} <: AbstractExpressionNode{T}
         return n
     end
 end
-@inline _data(x::Metadata) = getfield(x, :_data)
 
 """
     ParametricExpression{T,N<:ParametricNode{T},D<:NamedTuple} <: AbstractExpression{T,N}
@@ -79,15 +79,17 @@ struct ParametricExpression{
     metadata::Metadata{D}
 
     function ParametricExpression(tree::ParametricNode, metadata::Metadata)
-        return new{eltype(tree),typeof(tree),typeof(_data(metadata))}(tree, metadata)
+        return new{eltype(tree),typeof(tree),typeof(unpack_metadata(metadata))}(
+            tree, metadata
+        )
     end
 end
 function ParametricExpression(
     tree::ParametricNode{T1};
     operators::Union{AbstractOperatorEnum,Nothing},
-    variable_names,
+    variable_names=nothing,
     parameters::AbstractMatrix{T2},
-    parameter_names,
+    parameter_names=nothing,
 ) where {T1,T2}
     if !isnothing(parameter_names)
         @assert size(parameters, 1) == length(parameter_names)
@@ -200,18 +202,16 @@ function get_variable_names(
     ex::ParametricExpression,
     variable_names::Union{Nothing,AbstractVector{<:AbstractString}}=nothing,
 )
-    return variable_names === nothing ? ex.metadata.variable_names : variable_names
+    return if variable_names !== nothing
+        variable_names
+    elseif hasproperty(ex.metadata, :variable_names)
+        ex.metadata.variable_names
+    else
+        nothing
+    end
 end
-@inline _copy_with_nothing(x) = copy(x)
-@inline _copy_with_nothing(::Nothing) = nothing
 function Base.copy(ex::ParametricExpression; break_sharing::Val=Val(false))
-    return ParametricExpression(
-        copy(ex.tree; break_sharing=break_sharing);
-        operators=_copy_with_nothing(ex.metadata.operators),
-        variable_names=_copy_with_nothing(ex.metadata.variable_names),
-        parameters=_copy_with_nothing(ex.metadata.parameters),
-        parameter_names=_copy_with_nothing(ex.metadata.parameter_names),
-    )
+    return ParametricExpression(copy(ex.tree; break_sharing), copy(ex.metadata))
 end
 ###############################################################################
 
diff --git a/src/Strings.jl b/src/Strings.jl
index c4a3f0dd..f4dfa204 100644
--- a/src/Strings.jl
+++ b/src/Strings.jl
@@ -139,7 +139,7 @@ function string_tree(
     operators::Union{AbstractOperatorEnum,Nothing}=nothing;
     f_variable::F1=string_variable,
     f_constant::F2=string_constant,
-    variable_names::Union{AbstractVector{<:AbstractString},Nothing}=nothing,
+    variable_names=nothing,
     pretty::Union{Bool,Nothing}=nothing, # Not used, but can be used by other types
     # Deprecated
     raw::Union{Bool,Nothing}=nothing,
@@ -190,7 +190,7 @@ for io in ((), (:(io::IO),))
         operators::Union{AbstractOperatorEnum,Nothing}=nothing;
         f_variable::F1=string_variable,
         f_constant::F2=string_constant,
-        variable_names::Union{AbstractVector{<:AbstractString},Nothing}=nothing,
+        variable_names=nothing,
         pretty::Union{Bool,Nothing}=nothing, # Not used, but can be used by other types
         # Deprecated
         raw::Union{Bool,Nothing}=nothing,
diff --git a/src/StructuredExpression.jl b/src/StructuredExpression.jl
index 963da0e4..8b1550c3 100644
--- a/src/StructuredExpression.jl
+++ b/src/StructuredExpression.jl
@@ -16,7 +16,7 @@ import ..ExpressionModule:
     with_contents,
     Metadata,
     _copy,
-    _data,
+    unpack_metadata,
     default_node_type,
     node_type,
     get_scalar_constants,
@@ -114,7 +114,7 @@ constructorof(::Type{<:StructuredExpression}) = StructuredExpression
 function Base.copy(e::AbstractStructuredExpression)
     ts = get_contents(e)
     meta = get_metadata(e)
-    meta_inner = _data(meta)
+    meta_inner = unpack_metadata(meta)
     copy_ts = NamedTuple{keys(ts)}(map(copy, values(ts)))
     keys_except_structure = filter(!=(:structure), keys(meta_inner))
     copy_metadata = (;
@@ -143,7 +143,13 @@ function get_variable_names(
     e::AbstractStructuredExpression,
     variable_names::Union{AbstractVector{<:AbstractString},Nothing}=nothing,
 )
-    return variable_names === nothing ? get_metadata(e).variable_names : variable_names
+    return if variable_names !== nothing
+        variable_names
+    elseif hasproperty(get_metadata(e), :variable_names)
+        get_metadata(e).variable_names
+    else
+        nothing
+    end
 end
 function get_scalar_constants(e::AbstractStructuredExpression)
     # Get constants for each inner expression
diff --git a/test/test_expressions.jl b/test/test_expressions.jl
index 63f9a9a2..54448001 100644
--- a/test/test_expressions.jl
+++ b/test/test_expressions.jl
@@ -269,7 +269,7 @@ end
 
 @testitem "Miscellaneous expression calls" begin
     using DynamicExpressions
-    using DynamicExpressions: get_tree, get_operators
+    using DynamicExpressions: get_tree, get_operators, default_node_type
 
     ex = @parse_expression(x1 + 1.5, binary_operators = [+], variable_names = ["x1"])
     @test DynamicExpressions.ExpressionModule.node_type(ex) <: Node
@@ -278,6 +278,24 @@ end
 
     tree = get_tree(ex)
     @test_throws ArgumentError get_operators(tree, nothing)
+
+    # We can also define expressions without variable names, and it should work
+    operators = OperatorEnum(; binary_operators=[+])
+    for E in (Expression, ParametricExpression)
+        N = default_node_type(E)
+        kws = (; operators)
+        if E === ParametricExpression
+            kws = (; kws..., parameters=Matrix{Float64}(undef, 0, 0))
+        end
+        x1, x2 = (E(N(Float64; feature=i); kws...) for i in 1:2)
+        x1000 = E(N(Float64; feature=1000); kws...)
+        @test string(x1 + x2 + x1000) == "(x1 + x2) + x1000"
+        # And also with structured expressions
+        x1 = StructuredExpression(
+            (; x1, x2, x1000); operators, structure=nt -> nt.x1 + nt.x2 + nt.x1000
+        )
+        @test string(x1) == "(x1 + x2) + x1000"
+    end
 end
 
 @testitem "Expression Literate examples" begin
@@ -413,3 +431,26 @@ end
 
     #literate_end
 end
+
+@testitem "Expression with_metadata partial updates" begin
+    using DynamicExpressions
+    using DynamicExpressions: get_operators, get_metadata, with_metadata, get_variable_names
+
+    # Create an expression with initial metadata
+    ex = @parse_expression(
+        x1 + 1.5,
+        operators = OperatorEnum(; binary_operators=[+, *]),
+        variable_names = ["x1"]
+    )
+
+    # Update only the variable_names, keeping the original operators
+    new_ex = with_metadata(ex; variable_names=["y1"])
+    @test get_variable_names(new_ex, nothing) == ["y1"]
+    @test get_operators(new_ex, nothing) == get_operators(ex, nothing)
+
+    # Update only the operators, keeping the original variable_names
+    new_operators = OperatorEnum(; binary_operators=[+])
+    new_ex2 = with_metadata(ex; operators=new_operators)
+    @test get_variable_names(new_ex2, nothing) == ["x1"]
+    @test get_operators(new_ex2, nothing) == new_operators
+end